Radosgw port from upstream (WIP)

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Depends on https://github.com/crowbar/barclamp-ceph/pull/56
@mjura, what do you think? The only variable here should be service_name. But this is the way it is done in other recipes (osd.rb) and, more importantly, in upstream. Do we want to differ from upstream or do we want to eventually merge with them?
My opinion: I agree with @tboerger so I'd simplify it.