<oo-admin-check-sources.py> New tool for checking repo/subscription config

https://trello.com/c/sYLNUE8d/117-8-tool-needed-to-enforce-repo-compatibility-for-openshift

This tool uses the Yum API, so is written in Python. Some effort is
made to ensure compatibility with Python 2.6 and 2.7.

Implemented so far are

* repository priority checks and fixes for known "blessed"
  repositories

* some detection of potential repo conflicts and logic to fix those
  automatically

* functionality based on role (node, broker, etc.)

* minimal role-guessing

* missing repository/subscription detection

* etc.

TODOs include:

* add README

* whatever is outlined in the trello card but missing from this list