Make runtime less global for Codec

* Make Codec separate from Scheme
* Move EncodeOrDie off Scheme to take a Codec
* Make Copy work without a Codec
* Create a "latest" package that imports all versions and
  sets global defaults for "most recent encoding"
  * v1beta1 is the current "latest", v1beta2 exists
  * Kill DefaultCodec, replace it with "latest.Codec"
  * This updates the client and etcd to store the latest known version
* EmbeddedObject is per schema and per package now
* Move runtime.DefaultScheme to api.Scheme
* Split out WatchEvent since it's not an API object today, treat it
like a special object in api
* Kill DefaultResourceVersioner, instead place it on "latest" (as the
  package that understands all packages)
* Move objDiff to runtime.ObjectDiff

pkg/conversion/decode.go

@@ -25,14 +25,14 @@ import (
 // Decode converts a YAML or JSON string back into a pointer to an api object.
 // Deduces the type based upon the fields added by the MetaInsertionFactory
 // technique. The object will be converted, if necessary, into the
-// s.InternalVersion type before being returned. Decode will refuse to decode
-// objects without a version, because that's probably an error.
+// s.InternalVersion type before being returned. Decode will not decode
+// objects without version set unless InternalVersion is also "".
 func (s *Scheme) Decode(data []byte) (interface{}, error) {
 	version, kind, err := s.DataVersionAndKind(data)
 	if err != nil {
 		return nil, err
 	}
-	if version == "" {
+	if version == "" && s.InternalVersion != "" {
 		return nil, fmt.Errorf("version not set in '%s'", string(data))
 	}
 	obj, err := s.NewObject(version, kind)