Added three new modules for managing OVS, ODL and PCI devices. They
exist in the new charms_openstack/{sdn,devices} directories.
The modules have come from the
git@github.com:openstack/charm-openvswitch-odl.git charm and are
largely unaltered apart from new Doc strings and unit tests.
Change-Id: I3e44afeb866a7551883da04a699af3807853a83e
759530dabe