Save/Load registered notification phone number to db along with schedules

[devsdevsdevs]

This was moved to the backlog because it required more work in that we should prevent registration if someone hasn't loaded in their username.

[EricPedley]

Closing because no more AANTS, and when we do the rewrite we'll probably add the notifications stuff as part of the schedule anyways, which we already have code in place to prevent modifying before it's completely loaded.