Way early hacky PoC of object model silliness

This is entirely un-mergeable as it is, and is just for demonstrating
one way to do this. It's just hacked together enough to barely work.
Be nice :)

This adds nova/object.py (yes, I know we can't call it that), which is
a dumping ground for almost everything in the patch. It adds:

1. A NovaObject thingy which handles (de-)hydration stuff
2. A simple-minded implementation of the Migration object for demonstration
3. A subclass of RpcProxy that handles the magic (de-)serialization of
   NovaObject items over the wire, to avoid touching common bits.

It doesn't account for any RPC version changes that will need to be done.
Things are all dumped into object.py instead of where they should be.

Change-Id: Iecd54ca22666f730c41d2278f74b86d922624a4e