prompt: Delete Pivotal Tracker-related code

There was some unused code there, that was anyway not supposed to be
there. It goes into the PT module and it will be re-implemented in case
Pivotal Tracker becomes a supported issues tracker.

Story-Id: SF-98
Change-Id: 8b7ba5263b
Transfer the repo to salsaflow GitHub org

This requires the import paths to be fixed, and that is exactly what
this commit takes care of.

Change-Id: e9e53400a9
Story-Id: SF-98