Add authZ through incorporation of policy checks.
Add authZ through incorporation of policy checks.

Adds the policy openstack-common module and implements policy checks
for the v2 API.  Note that this cut only addresses whole objects (i.e.,
a subnet or a network or a port), not specific fields within objects.
(This means that attributes are not filtered out based on policies.)
Implements blueprint authorization-support-for-quantum.

Change-Id: I1b52b1791a1f14f0af6508a63a40a38e440f15fe

citrix-openstack-build/neutron-lbaas,flavio-fernandes/networking-odl,openstack/neutron-fwaas,citrix-openstack-build/neutron-fwaas,gandelman-a/neutron-lbaas,dougwig/x-neutron-fwaas,CiscoSystems/networking-odl,gandelman-a/neutron-lbaas,gotostack/neutron-lbaas,gaolichuang/neutron-fwaas,openstack/networking-odl,gotostack/neutron-lbaas,dougwig/x-neutron-lbaas,flavio-fernandes/networking-odl,openstack/neutron-vpnaas,dougwig/x-neutron-vpnaas,gotostack/neutron-lbaas,gaolichuang/neutron-fwaas,CiscoSystems/networking-odl,gandelman-a/neutron-lbaas,mestery/x-stackforge-odl,FedericoRessi/networking-odl,openstack/neutron-fwaas,schoksey/networking-odl,citrix-openstack-build/neutron-vpnaas,openstack/networking-odl,openstack/networking-odl,openstack/neutron-vpnaas,FedericoRessi/networking-odl,schoksey/networking-odl