Enable a configurable whitelist of namespaces for V22

If a namespace is present in the whitelist, all calls are sent to the OCI model instead of the Pre OCI model

Note that this does increase overhead for registry calls (since we need to lookup the namespace for every single call), but it should only be temporary until we've migrated all users over to the OCI data model

data/registry_model/interface.py

@@ -269,7 +269,7 @@ class RegistryDataInterface(object):
 
   @abstractmethod
   def lookup_blob_upload(self, repository_ref, blob_upload_id):
-    """ Looks up the blob upload withn the given ID under the specified repository and returns it
+    """ Looks up the blob upload with the given ID under the specified repository and returns it
         or None if none.
     """