Push endpoint

READY FOR MERGE

Add endpoints for ``push`` / ``result_sets`` and for ``results`` for jobs.
* prevent duplicates of mapping ``result_sets`` to ``revisions``.
* Add new endpoints for ui:
    * ``get_result_set_list`` - Returns a list of result_sets / pushes.  Used by the UI to get the list of pushes to display.  Accessed from endpoing ``/resultset/``
    * ``get_result_set_job_list`` - Get a specific result set.  this will also return the applicable job results for that result_set.  Accessed by endpoint ``/resultset/<id>/``
    * ``get_result_set_by_id`` - Get a single result set by id, then add the job list to it in the viewset.