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)
Prepares for the meta object to front multiple underlying types
when TypeMeta and ObjectMeta is split in internal and v1beta3, but
combined in v1beta1 and v1beta2