Prepare for running multiple API versions on the same HTTP server
by decoupling some of the mechanics of apiserver. Define a new
APIGroup object which represents a version of the API.
* Add labels selector (same as List)
* Add fields selector
* Plan to let you select pods by Host and/or Status
* Add resourceVersion to let you resume a watch where you left off.
The apiserver on initialization must be provided with a codec
for encoding and decoding all handled objects including api.Status
and api.ServerOp. In addition, the RESTStorage Extract() method
has been changed to New(), which returns a pointer object that the
codec must decode into (the internal object). Switched registry
methods to use pointers for Create/Update instead of values.
