[fix bug 1055563] Initial db table for the action items.

* Migrate reps and mozillians dashboard in a new app.
That was my initial approach. The reason I chose to encapsulate these inside the class at the first place is because this is more flexible: Eg we can use `ActionItem.Major` and have a different priority assigned to the Major label for action items compared to notifications. The downside is the duplicate code. I don't have strong feelings though. Thoughts?