Build packages for client and yum repositories

As discussed at Madrid workshop.

Fixes #16.
Fixes #17.
this is not ok. we really need a repo with a `$releasever` , and maybe a second `externals` repo that is truly cross-OS like the quattor one.
same for aquilon repo imho (since it's python, i'm assuming the rpms have the python version in the packge path)?