Decouple apiserver from codec implementation

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.
Merge pull request #807 from smarterclayton/abstract_apiserver_encoding

Decouple apiserver from codec implementation