This introduces driver for Vmware NSX Policy.
The driver assumes nsx_v3 core plugin.
It implements direct configuration of NSX Policy endpoint for security
and inherits connectivity functionality from resource mapping driver.
On startup, the driver will configure NSX Policy enforcement point to be
the NSX manager core plugin is running against.
The driver implements the following resource mapping:
Openstack project => NSX Policy domain
GBP group = > NSX Policy group + communication maps
GBP classifier => NSX Policy service
GBP rule set => NSX Policy communication profile
Change-Id: I0d5593b458f7e51c21fc2b34d1ab4d898abb6c51