(PUP-3119) Added yaml output to puppet resource

This enables you to list resources in YAML format for copy/paste into Hiera files.

The output should be suitable for use with the create_resources function
Oh, that's even better then. We could fix `to_manifest` and friends in one go.

I guess that should happen in a `maint` change. Could even be postponed to a dedicated branch, as far as I'm concerned.