Remove unnecessary param from defaultNamespace()

The `clientConfig` param currently being passed is not needed, because
it exists as a package level var in root. It also makes little sense to
pass a custom `clientConfig` because if `overrides.Context.Namespace` is
populated, the namespace that is returned is configured as an override
in the package level `clientConfig` and not the `clientConfig` in the
param.

Remove client-go flags from commands that don't use

Add arg length constraint to commands

Construct base components Obj

In order to support environment heirarchy, we need to be able to
reference all components. This commit will implement component imports
as k-v pairs ex: foo: "import/foo.jsonnet" as a Jsonnet object. This
jsonnet object will then be assigned as an ExtCode so that it can be
referenced by a base.libsonnet file which environments can build /
override upon.

Fix 'env set' where --name flag is not specified

There is a bug where if --name is not passed during env set, an error is
thrown due to failed validation checking on an empty name. This commit
fixes this bug.

Add combination deployment/service system prototype

Implement 'prototype preview'

Currently the command 'prototype use' expands a prototype and prints to
stdout. This is useful, but most of the time, users want to simply dump
the result in 'components/'

This command implements this print-to-stdout behavior in a new command,
'prototype-preview', and reimplements 'prototype use' to drop the
expanded prototype into 'components/'.

The new form of this command is:

  ksonnet prototype use <prototype-name> <component-name> [type] [flags]

So, for example, a command like:

  ksonnet prototype use deployment nginx-depl [...]

would expand the 'deployment' prototype, and place it in
'components/nginx-depl.jsonnet' (since Jsonnet is the default template
expansion). Alternatively, something like this:

  ksonnet prototype use deployment nginx-depl yaml [...]

would expand the prototype and place it in 'components/nginx-depl.yaml'
(assuming that there is a YAML version of this template.

Currently `metadata.isValidName` will admit names that should be invalid
(e.g., names with spaces, leading '/' characters) and not admit names
that should be valid (e.g., names with '.' characters inside).

This commit moves this function into `metadata/interface.go` and hardens
it against these constraints.

Add help docs for `delete`

Fixes #132.

Add example to the service prototype's documentation

Add `prototype list` command

Fixes #108.

The `prototype list` command lists all known prototypes. It is
functionally equivalent to a `prototype search` that returns all
prototypes.

Cause `init` to generate env using current-context

When we run `init`, currently we generate a simple environment called
'default' with no URI. A better idea is to generate the URI from the
current context of the active kubeconfig file, if it exists.

Fix improper elision of -J flags

Set default log level to 'Info'

Currently if we use a command like `apply default -f
components/whatever.yaml`, kubecfg will fail to emit flags that add
ksonnet-lib to the -J paths. This means that, while a command like
`apply default` will correctly linke against (e.g.) `k.libsonnet`,
adding the `-f` flag will not.

This commit will correct this problem for all commands of this form.

Commands using the <env> arg should deploy to the correct cluster

For example, 'apply <env' currently operates as a no-op. With the
introduction of simple environments in PR #131, 'apply <env>' should
perform basic validation such that:

1. The user has added the environment that is being deployed against to
their Ksonnet project.

2. The URI in the environment's spec file that the user wishes to deploy
to should correspond to at least one cluster location as listed in
kubeconfig.

If either of those conditions are not satisfied, the kubecfg user will
receive the corresponding error.

In addition, this commit will set the kubectl --cluster flag to point at
the cluster listed by the environment URI.

Currently, commands take either an <env> or a '-f' argument but not
both. With this commit, we are allowing both args to be provided. The
behavior is expand the files passed by the '-f' flag and deploy the
objects to <env>.

Adopt 0755 as default permissions for folders

Under certain circumstances, it is possible for operations to fail
because of permissions that are too restrictive. Here we adopt the
default permissions of 0755 (i.e., rwxr-xr-x), which should be a better
balance of restriction and flexibility.

Add logging to 'env' subcommands

This commit will add logging to all env subcommands 'list', 'set',
'add', and 'rm'. It adds both Info level and Debug level logging.

Fixes #137

Add to 'env' command documentation

Currently 'Info' level logs are only shown with the '-v' flag. This
makes commands without the '-v' flag of little use to users, especially
on success cases, due to no output.

This commit will set the default log level to 'Info', and passing a '-v'
flag will log at a 'Debug' level.

Fixes #139.

Set default permissions in `metadata.Manager` to 0644

Currently all files and folders created with the `metadata.Manager`
(which is the core FS management subsystem) are created with permissions
0777, i.e., everyone has all permissions.

This commit transistions us to a more locked down permissions set, 0644,
which allows the user to do everything except execute, and everyone else
to only read.

Since we don't store any app code that needs to be executed, this should
be suitable for everything.

Fixes #136.

Introduce env subcommands 'env add', 'env rm', 'env set' & 'env list'