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
Somewhere I thought I replied about making it easier to select out this group of fields in queries (GET ...?field=metadata), but I can't find that comment now.

Also, while Go appears to support inlining reasonably well even without Generics, I imagine that dealing with the metadata fields generically across object types without a common subobject may be challenging in some client languages.

However, it's probably not super-critical either way, and I don't want to bikeshed about this forever. If we do inline these fields, then I'm going to insist that we inline nothing else -- all other fields must be in subobjects.