controller for the endpoint policy extension

The controller level of the extension is really just a
marshalling function, with the exception that it is responsible
for catching any delete notification events for the entities
that are part of endpoint policy associations.

Implements: bp endpoint-policy
Change-Id: I4c5e9e9cff392f917a9d79a798ff72df2f48e6d1
Merge "controller for the endpoint policy extension"