blueprint mellanox-quantum-plugin

Implements Mellanox Quantum plugin.
This plugin implements Quantum v2 APIs with support for Mellanox embedded
switch functionality as part of the VPI (Ethernet/InfiniBand) HCA.

Change-Id: I22907dfec5b6cb8f6ad8c3b6e390abc4f8e0ac10
add db to save host for port

blueprint portbinding-ex-db

related patch in nova:
https://review.openstack.org/#/c/21141/

Only OVS and linux bridge plugins now support this feature.

Change-Id: I42d9bc59130e2758dd6a221d8953d63ec10e1f3c
Merge "add db to save host for port"