Add support for direct pushing of schema 2 manifests without tags

This is required for manifest lists

data/registry_model/interface.py

@@ -303,3 +303,10 @@ class RegistryDataInterface(object):
   @abstractmethod
   def get_schema1_parsed_manifest(self, manifest, namespace_name, repo_name, tag_name, storage):
     """ Returns the schema 1 version of this manifest, or None if none. """
+
+  @abstractmethod
+  def create_manifest_with_temp_tag(self, repository_ref, manifest_interface_instance,
+                                    expiration_sec, storage):
+    """ Creates a manifest under the repository and sets a temporary tag to point to it.
+        Returns the manifest object created or None on error.
+    """