LBaaS Agent Reference Implementation

implements blueprint lbaas-namespace-agent

This a reference implemention of the Quantum load balancing service
using HAProxy.  The implemention is designed for vendors, developers,
and deployers to become familiar with the API and service workflow.

This change also adds some constraint checks for data integrity.

Change-Id: I10a67da11840477ccf063b98149f4f77248802a1
Merge "LBaaS Agent Reference Implementation"