ML2 Mechanism Driver for Tail-f Network Control System (NCS)

Define a new ML2 Mechanism Driver that replicates Neutron network/port
configuration changes to NCS: http://www.tail-f.com/network-control-system/

Configuration is sent using a HTTP/JSON interface.

Implements blueprint tailf-ncs

Change-Id: I1f73fa3f2e4eec8e5a0f2865aec2d934e25c76d1
Merge "ML2 Mechanism Driver for Tail-f Network Control System (NCS)"