Add backend processor for AMQP

Backend processors execute the ReST API using a specific backend.  For
example, docker implements the container backends.  k8s implements the pod
and services backends.  If at some later date, someone wants to implement
a fully native backend, that would be possible.  In the short term (next 4-6
weeks) I'd like to focus on backends using k8s and docker only rather then
trying to get native to work.

Change-Id: I77abde65dfe03e12f2931854da52a69f5e618d93
Merge "Add backend processor for AMQP"