Add SkaffoldYamlGenerator.

[coollog]

This class should generate a skaffold.yaml with some degree of customization, but mostly to support the case of:

apiVersion: skaffold/v1alpha2
kind: Config
deploy:
 kubectl:
   manifests:
   - MANIFEST_PATH

This class should generate the YAML as a String to be able to be passed via stdin to skaffold <command> -f -.

[TadCordle]

I figure the only configuration option we need is a List<Path> manifestPaths, at least to start out. Is there a default directory we're going to use for these?

[coollog]

Yea, that sounds good. No default directory is necessary since any defaults chosen will be outside the scope of this generator.