Added basic interface for authorizer implementations.
Added default "authorize everything" and "authorize nothing
implementations.
Added authorization check immediately after authentication check.
Added an integration test of authorization at the HTTP level of
abstraction.
PUT allows an object to be created (http 201). This allows REST code to
indicate an object has been created and clients to react to it.
APIServer now deals with <-chan RESTResult instead of <-chan runtime.Object,
allowing more data to be passed through.