Add Neutron l3 metering agent
Add Neutron l3 metering agent

This is the agent side of :
blueprint bandwidth-router-measurement
blueprint bandwidth-router-label

This patch initiates agent side by adding a new
l3 metering agent and a Noop Driver.

DocImpact

Change-Id: Ib34721209c282b2669ff5488a33293d9f86467ef

FedericoRessi/networking-odl,openstack/networking-odl,openstack/networking-odl,FedericoRessi/networking-odl,flavio-fernandes/networking-odl,CiscoSystems/networking-odl,schoksey/networking-odl,flavio-fernandes/networking-odl,mestery/x-stackforge-odl,openstack/networking-odl,CiscoSystems/networking-odl,schoksey/networking-odl