[openstack-full] add prod/monitoring/backup/log packages a cleaner way

  * packages installation is now role-based
  * remove some duplicate packages which were already in base or openstack-common
  * only Debian is covered by those production packages for now
In fact, all this repository stuff surely have to move here : https://github.com/enovance/edeploy/blob/master/build/repositories

Note this code is only taking care of a particular debian distro (wheezy) while it shall use $DIST to support any other.