Wire API models to policy engine

Previously, the API was wired to dummy data models.  We now initialize
the policy engine and API together from congress_server.py

Note: you must set the policy_path param in
congress/etc/congress.conf.sample for the server to work properly.

Change-Id: I6ae855fc217dc2401035b6c9f89d1d6607f8ac10
Merge "Wire API models to policy engine"