Define and wire in bulk flow update adapter API

This adds support for defining bulk or incremental
flow update capability on a per device type basis
and implements the callout mechanism.

It also defines 5 new API entries for proxying
messages from a child-device adapter (e.g. ONU adapter)
to the actual device as well as the APIs for registering
and receiving async messages from a device via a
parent device acting as a proxy. The implementation
of this is left for the next PR.

Change-Id: Ic48a458c170083842b6bc674d675b5b60c0827f6
diff --git a/voltha/core/adapter_agent.py b/voltha/core/adapter_agent.py
index 319f084..5659f85 100644
--- a/voltha/core/adapter_agent.py
+++ b/voltha/core/adapter_agent.py
@@ -127,6 +127,13 @@
     def deactivate_device(self, device):
         return self.adapter.deactivate_device(device)
 
+    def update_flows_bulk(self, device, flows, groups):
+        return self.adapter.update_flows_bulk(device, flows, groups)
+
+    def update_flows_incrementally(self, device, flow_changes, group_changes):
+        return self.update_flows_incrementally(
+            device, flow_changes, group_changes)
+
     # ~~~~~~~~~~~~~~~~~~~ Adapter-Facing Service ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
     def get_device(self, device_id):