Typo in conversion Godoc
Begin to unify ResourceVersioner and SelfLinker

Create a new MetadataAccessor interface that combines both
and use it where previously latest.ResourceVersioner and SelfLinker
were being used.

Adds Namespace to the get/set interface. Adds TODO about future
fast path for metadata (as per thockin's comment)
Merge pull request #2009 from smarterclayton/unify_meta

Unify Accessor for ObjectMeta/TypeMeta/ListMeta