Support content-type negotiation in the API server

A NegotiatedSerializer is passed into the API installer (and
ParameterCodec, which abstracts conversion of query params) that can be
used to negotiate client/server request/response serialization. All
error paths are now negotiation aware, and are at least minimally
version aware.

Watch is specially coded to only allow application/json - a follow up
change will convert it to use negotiation.

Ensure the swagger scheme will include supported serializations - this
now includes application/yaml as a negotiated option.

pkg/apiserver/resthandler_test.go

@@ -28,6 +28,7 @@ import (
 
 	"k8s.io/kubernetes/pkg/api"
 	apierrors "k8s.io/kubernetes/pkg/api/errors"
+	"k8s.io/kubernetes/pkg/api/testapi"
 	"k8s.io/kubernetes/pkg/api/unversioned"
 	"k8s.io/kubernetes/pkg/apimachinery/registered"
 	"k8s.io/kubernetes/pkg/runtime"
@@ -155,7 +156,7 @@ func (tc *patchTestCase) Run(t *testing.T) {
 	namespace := tc.startingPod.Namespace
 	name := tc.startingPod.Name
 
-	codec := registered.GroupOrDie(api.GroupName).Codec
+	codec := testapi.Default.Codec()
 	admit := tc.admit
 	if admit == nil {
 		admit = func(updatedObject runtime.Object) error {