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/genericapiserver/genericapiserver_test.go

@@ -94,6 +94,7 @@ func TestInstallAPIGroups(t *testing.T) {
 	config.ProxyTLSClientConfig = &tls.Config{}
 	config.APIPrefix = "/apiPrefix"
 	config.APIGroupPrefix = "/apiGroupPrefix"
+	config.Serializer = latest.Codecs
 
 	s := New(&config)
 	apiGroupMeta := registered.GroupOrDie(api.GroupName)