Split quantum into server/agent elements.

Compute nodes will need the agent, but do not want the whole
quantum-server running.

Change-Id: I6b899d816956a4c953d747d070b27e9599a86081
Make public interface configurable.

Change-Id: Iff0845628ce4f90c74fc891511f8d1aa6439de0d
Merge "Split quantum into server/agent elements."
Merge "Make public interface configurable."