Add ceph::repo and it's unit tests to puppet-ceph

ceph::repo is used to set up official ceph repositories.
This commit brings support for the Ubuntu LTS and Debian operating
systems.
It also allows the cuttlefish and the dumpling release of Ceph.
Redhat-like support is planned.

Closes-bug: #1243348
Change-Id: I667acebdd94d0644006e5775962a25e6280e6896