GitLab

For consistency with other options (hyphenated, not camel case), and
the upstream `jsonnet` tool.

Add a new native function that resolves docker image names into more
specific forms.  In particular, it can look up a docker registry and
convert image:tag to image@digest at jsonnet-eval time.

Limitations: Does not currently support private docker
registries (that require authentication).

Controlled via two new command line flags:
- `--resolve-images` Change implementation of resolveImage native
  function. One of: noop, registry (default "noop")
- `--resolve-images-error` Action when resolveImage fails. One of
  ignore,warn,error (default "warn")

Note in particular that the defaults will *not* do remote registry
lookups, and will only add an explicit ":latest" tag where no tag was
given.

Fixes #13

Fixes #12

Rename early and often.

- Support the standard client-go/kubectl flags
- Switch object types to use client-go rather than apimachinery
- Implement update subcommand

File format is recognised via simple file extension check.

Any "List" objects found will be expanded into their constituent
items, so single-element formats like json and jsonnet can use a
v1.List to capture multiple resource objects.

Basic skeleton.  Can evaluate jsonnet and show the output as yaml or
json .. and that's about it.