Added script to manage repositories

Quite big script, here's what it can do right now:
* Sign packages in batch mode (passing passphrase as parameter)
* Create/update rpm repos using multiple sources, passed as arguments or in a
  configuration file:
    · From jenkins url (multijob or simple job)
    · From koji url
    · From a url with rpm links on it, recursively or not (rec: prefix for
      recursive)
    · From a directory, all packages (dir: prefix)
    · From a directory only the latest packages (latest: prefix)
* Remove the old rpm versions and keep only the N newest
* Run createrepo in a multidistro repository (runs on each distribution subrepo)
* Generate source tree from src.rpms in the repo
* Sign source files (detached ascii armored signature)

I tried to keep the output informative and human readable, but mostly to be run
on jenkins jobs.

Change-Id: Ib630eb1e3b701eaf224451f02692723447aa1f8b
Signed-off-by: David Caro <dcaroest@redhat.com>