Add support for the Nexus 1000V into the Cisco Plugin.

Add support for the Nexus 1000V into the Cisco Plugin.

This will enable the Cisco Nexus 1000V to integrate with the Cisco plugin
and be used to drive the realization of Neutron constructs.
Network profile and Policy profile are introduced as extended neutron
resources, while n1kv:profile_id is introduced as an extended attribute
for network and port objects. Necessary changes to the Cisco plugin are
made to accomodate Nexus 1000V as a configurable vswitch plugin.

Implements: blueprint cisco-plugin-n1k-support
Change-Id: I951e10c57d74c935fca8754c0e21e1ac9df35704