Add types for prototype parameters

Fix #113

When a user runs `prototype search`, we'd like for the output to include
the name, description, and available template types, and we'd like that
output to be padded for readability. For example, if the user runs
`prototype search io.`, we'd like to output something like this:

   io.whatever.pkg.foo    Foo's main template    [jsonnet, yaml]
   io.whatever.pkg.foobar Foobar's main template [jsonnet,   yaml, json]

This commit will introduce this style of padded output to the `prototype
search` subcommand.

This commit will fix #116 by introducing two new constructs to the
prototype specification schema:

1. Mandatory types for prototype parameters. This lets us accept bare
   words on the command line, and then "do the right thing" when
   emitting JSON or Jsonnet.

   For example, say a template produces a `core.v1.Service` that exposes
   a port with a `--targetPort` flag. When the user passes a number
   (e.g., `80`) in, we should _not_ put quote marks around it, since we
   want to expose port `80`. When the user passes a string (e.g.,
   `"nginxPort"`), we _should_ put quote marks around it, to denote that
   we're exposing the port with that name.

   In order to do this, we need to know they "type" of the parameter (in
   this case, `NumberOrString`).

2. Mandatory template types. A template can have a JSON, YAML, or
   Jsonent flavor, and we default to using Jsonnet. This is useful
   mostly to make type parameters less error-prone (since one set of
   parameters corresponds to one set of templates), but it also
   significantly de-bloats the output of commands like `search`, since
   one fully-qualified name can correspond to multiple flavors of the
   same template.

This commit fixes #113, causing us to emit `k.libsonnet` (a collection
of extensions to the k8s API) by updating the dependency on
`ksonnet-lib/ksonnet-gen` and exercising the new signature for
`ksonnet.Emit`, which handles this automatically.

We update the `vendor/` directory and the code that depends on it in the
same commit so that we don't break bisect.

'init' should use current directory when generating Ksonnet app

Change directory structure generated by 'init' to support envs

This commit will remove the vendor/lib and vendor/schema directories
generated by 'init'. An 'environments' directory will be created from
the root app directory, with the default environment directory 'dev'
and it's containing contents rooted at 'environments'.

The intention of environments are to represent the deployment
environments of Kubernete clusters, with the following example
directory structure:

app-name/
  ..
  envs/
    dev/
    us-west/
      prod/
      staging/

Support import param rewrite for jsonnet snippets

Deprecate `update` subcommand; introduce `apply`

This commit is a follow-up to the discussion in the ksonnet.next design
doc, in which users consistently expressed their preference that the
`update` command be called `apply`.

NOTE: We have renamed `pkg/kubecfg/update_test.go` ->
`pkg/kubecfg/apply_test.go`, but we copy the `update`'s integration test
file. The reason is that the `update` unit tests actually test things
like GC (rather than the command itself), so the file name is
inconsequential. On the other hand, the integration tests test the
commands themselves, so it is important to have two copies, one for
`update` and one for `apply`.

This commit will rewrite all parameters in the passed Jsonnet file of
the form `import param://foo` to `${foo}`. This will be a utility for
`ksonnet prototype use` to support LSP-spec-compliant snippet JSONs.

Include `lib/` and `vendor/lib` when expanding templates

Currently, if the user wants to deploy a ksonnet application, and that
application uses some vendored library, or something in the `lib/`
directory, they will have to pass the appropriate `-J` flags into the
command themselves.

This commit will automatically add these whenever we're in an app
directory and a command is issued. In particular, even if the user
passes in the `-f` flag (rather than an environment name), we'll still
add library paths to the command if we're in a ksonnet app directory.
This is meant to capture the case that a user wants to update one
resource in particular in a ksonnet application.

Disable yaml case until test can be rewritten

show_test has been failing intermittently since
af3f0f6c introduced `-f`.

The test failure is due to the flags not being completely reset
between `RootCmd.Execute()` invocations, thus the second of json/yaml
(changes because hash ordering) sees *duplicate* `-f` options, and
produces duplicate output.  This breaks json test validation, but
not yaml(!)

Ideally we would revert the offending change and resubmit with fixed
tests, but there have been numerous changes merged since. To stop
developing _further_ failure blindness, this change simply disables
the (less-strict) yaml testcase while a rewrite of show_test is
undertaken (probably a move to new integration framework).

This is *not* a fix for #99

Allow explicit --namespace to override value in kubeconfig context

This has been a frequent area of client-go bugs, so add tests that
exercise --namespace handling in various scenarios.

If the current kubeconfig context is declared with an
explicit (non-empty) namespace, then `mergedKubeConfig.Namespace()`
returns that *config file* namespace value, ignoring an explicit
`--namespace` command line flag.

See https://github.com/kubernetes/client-go/issues/288 for upstream
client-go bug/discussion.

This change works around the issue by just checking the Namespace
override ourselves before falling through to the regular function.

Further fixes #103

Revert "Remove kubectl and Jsonnet flags from commands that don't use…

This reverts commit 020d5da0.

The change broke --namespace (and other flag) handling, because it
recreates the `clientConfig` global singleton multiple times - only
some of which are correctly tied to the relevant flags.

Introduce initial version of the `prototype` command

This commit implements `prototype` and its subcommands (i.e., `use`,
`search`, and `describe`) as specified in the ksonnet.next design doc.

This commit will introduce a simple skeleton of the `prototype` package,
which will (eventually) form the basis of the prototype command
(including the `search`, `describe`, and `use` subcommands as dictated
by the specification).

The Language Server Protocol (LSP) implements TextMate's "snippets"
feature. Originally imagined as a kind of Mad Libs for code, with users
given a code template and some number of "placeholder" blanks to fill
out, which was done by using tab to switch between them, LSP team
attempted to standardize this feature across language servers, so that
language authors had a well-specified interface to provide "snippets" to
any editor implementing the LSP.

Today, the LSP specification of TextMate snippets forms the bedrock of the
ksonnet prototype specification. Specifically, though users will
eventually be able to use Jsonnet to generate prototypes, they are
compiled down to the TextMate snippets specification.

This commit begins this process by introducing an implementation of the
LSP snippets specification, including both a parser and an evaluator.

For more details, see the extensive comment in `interface.go`.

Refactor cmd/ application logic to pkg/

This commit will separate the application level logic for the 'show', 'delete',
'validate', and 'diff' commands from the Cobra logic in the cmd/ package.  The
application level logic will be placed in pkg/kubecfg/.

fix integration tests

The integration commit (#90) raced with another (#80) that changes the
`kubecfg` command line.  This commit adds the newly-required `-f` flag.

Add basic integration test framework

Fix README

Now the commands take either an env or a file, so let's at least fix the
README to make it work with files.

Implement `init`; bring synchronization primitives to spec

The ksonnet.next design doc specifies the core kubecfg verbs (i.e., the
ones listed above) to all have the form:

  kubecfg <verb> [<env-name>|-f <file-or-dir>]

That is to say, each of these should be able to take either an
environment name, or a `-f` flag with a list of files and directories to
apply `verb` on. In the case of the environment, we will apply `verb` to
every component in the `components/` directory.

This commit implements this behavior for all these verbs.

This commit will introduce the ability of the `metadata.Manager` to
report every file in the `components/` directory.

This is primarily useful when we invoke the Jsonnet VM, as it requires a
list of files to expand. (The `template.Expander` also handles YAML and
JSON.)

This commit will introduce the `template.Expander` abstraction, which is
meant to abstract over an invocation of the Jsonnet VM. Specifically, it
provides facilities for users to provide (e.g.) Jpaths, ext vars, and so
on.

The main justification for this change is:

* We need a common way for the `pkg` and `cmd` packages to interact with
  the Jsonnet VM.
* The `utils` package is already too much of a catch-all.
* It's easier to think about an invocation of the Jsonnet VM when we
  additionally encapsulate the parameters we pass to it on every
  invocation in kubecfg.