Make unversioned.ListMeta implement List. Update all the *List types so they implement GetListMeta.
This helps avoid using reflection to get list information.
Remove all unnecessary boilerplate, move the interfaces to the right
places, and add a test that verifies that objects implement one, the
other, but never both.
Remove Codec from versionInterfaces in meta (RESTMapper is now agnostic
to codec and serialization). Register api/latest.Codecs as the codec
factory and use latest.Codecs.LegacyCodec(version) as an equvialent to
the previous codec.
