Proposal: v1beta3 API overhaul

Speculative change for some items from #1200:

* Metadata that applies to resources is split from APIMetadata on non-resource API objects
* Metadata is a sub field of objects
* Labels are on Metadata
* Pod current and desired state is split
* Name is used for pods instead of ID (UID is part of metadata, Name is part of resource) for idempotent creation #148 and #1216 
* PodTemplate is a Metadata carrying object as per #170
 * If replicationController gave way to a generic "replicator", then pod template could be both a nested struct and a real resource.
* A ScheduledPod and ScheduledPodList is what the kubelet sees as per #860
* Non-schema'd k/v values on Metadata as `Config` (better names welcome) as per #1201

Not changed yet:

* ReplicationControllers
* Services

EDIT: Moving to higher bandwidth document here: https://docs.google.com/document/d/1E_HNsbyocweD9zJHXbz5Xb9XPwBqvDnLHhGeBq15FlI/edit?usp=sharing
I'm fine with changing emptyDir to EmptyDirectory or even just "empty".

hostDir is interesting - it doesn't have to be a directory at all - it can be a host file.  Maybe it should just become hostMount or fromHost or something. 

I don't think v1beta3 needs to block on either of these - I think we can make a compatible change here.