Group Policy Mapping DB-1: EP, EPG, L2 Policy, L3 Policy

(Patch series identifier: GPM-DB-1)

This patch extends the DB layer for the initial set of Group Policy
API resources with attributes mapping those resources to traditional
Neutron resources. Subsequent patches will add the plugin and driver
support for the mapped resources.

Author:            Bob Kukura <kukura@noironetworks.com>
Co-Authored-By:    Sumit Naiksatam <sumitnaiksatam@gmail.com>
Co-Authored-By:    Stephen Wong <s3wong@midokura.com>
Co-Authored-By:    Mohammad Banikazemi <mb@us.ibm.com>
Co-Authored-By:    Mandeep Dhami <dhami@noironetworks.com>

Change-Id: Ifa2d958035567881b1b4b515743dede0b8acde40
Merge "Group Policy Mapping DB-1: EP, EPG, L2 Policy, L3 Policy"