Populate ActionItem model from bugzilla, polls and events.

* Sync [waiting <item>] action items from bugzilla.
* Sync pending_mentor_validation action items from bugzilla.
* Sync budget_needinfo action items from bugzilla.
* Sync council reviewer assignment action items from bugzilla.
* Change ActionItem model fields.
* Create action items only for bugs assigned to Reps.
* Add new action item on new poll.
* Resolve action item on new vote.
* Add new action item to submit post event metrics.
* Resolve action item when post event metrics are submitted.
If a ``needinfo`` flag is removed it is probably because the info was somehow given (thus resolving as complete the action item). If a bug is marked as RESOLVED the action item for needinfo is going to be marked as ``resolved`` but not ``completed``.