Add ceilometer 6.0.0

 * Update runtime requirements according to global requirements of Mitaka
 * Update build depends according to test requirements of the project
 * d/ceilometer-common.install:
   - Remove gabbi_pipeline.yaml
     because it's only for tests
   - Remove gnocchi_archive_policy_map.yaml
   - Add ceilometer-config-generator.conf
 * Synchronize build scripts from Debian.
   Source: https://anonscm.debian.org/git/openstack/ceilometer.git
   Commit: c7caa6f0ab1349e09745c17c600eb6b5d7532e4f

Change-Id: I6a16629bec5be9f39e158e46e9079415551e46f8