Switch to pbr.

Use pbr instead of openstack.common.setup|version per Havana Summit.

Fixes bug 1179007

Change-Id: Ife7194cfd3f4444d7006fdf90b79be77737abd0a
Use sqlalchemy session code from oslo.

The session code in ceilometer was copied in from an old version of
nova which has since fallen out of date.

Change-Id: I6de3d6488a0cfe5943db144ca2f4924a2bfb8310
Merge "Switch to pbr."
Merge "Use sqlalchemy session code from oslo."