Add a ceph::client class

That should be used to configure clients without using exported
resources.
Anyway …
```
$ git grep ç
LICENSE:    François Charlier <francois.charlier@enovance.com>
manifests/apt/ceph.pp:#  François Charlier francois.charlier@enovance.com
manifests/conf.pp:#  François Charlier francois.charlier@enovance.com
manifests/mds.pp:#  François Charlier francois.charlier@enovance.com
manifests/mon.pp:#  François Charlier francois.charlier@enovance.com
manifests/osd.pp:#  François Charlier francois.charlier@enovance.com
manifests/osd/device.pp:#  François Charlier francois.charlier@enovance.com
manifests/package.pp:#  François Charlier francois.charlier@enovance.com
```