Adds a Hyper-V Quantum plugin

Adds a Hyper-V Quantum plugin

Blueprint quantum-plugin-hyper-v

Initial Hyper-V Quantum plugin including VLAN support.
Support for NVGRE networking will be added in a subsequent patch.
The plugin architecture relies heavily on the OVS plugin, with some
design differences to handle different network types via polymorphism.

The plugin contains two main components:

The plugin itself, to be executed on Linux or Windows
The L2 agent, to be executed on each Hyper-V node

L3 networking is currently handled on Linux with the existing agents.

A Nova Quantum Vif plugin is included in the Nova project.

Change-Id: Ie64bff448e3fb1129c5e24baaf148cdcc0aed8b9