Automatic merge from submit-queue

Adding support objects for integrating dynamic client the kubectl builder

Kubectl will try to decode into `runtime.VersionedObjects`, so the `UnstructuredJSONScheme` needs to handle that intelligently.

Kubectl's builder also needs a `meta.RESTMapper` and `runtime.Typer`. The `meta.RESTMapper` requires a `runtime.ObjectConvertor` (spelling?) that works with `runtime.Unstructured`. The mapper and typer required discovery info, so I just put that in the kubectl util package since it didn't really seem to fit anywhere else. 

Subsequent PRs will be using these in kubectl.

cc @kubernetes/sig-api-machinery @smarterclayton @liggitt @lavalamp