Instead of requiring iteration to be able to list new
jobs and existing jobs so that they can be claimed, allow
for attaching callbacks to the jobboard where instead of
requiring iteration those callbacks will be automatically
called by the jobboard internally when events are recieved.
Breaking change: renames transition notifier to notifier
since it is really not just a notifier for transitions but
is a generic notifier of events occuring (and details about
those events). This is an internal api so its not expected
that this will cause any issues (it's not expected for external
users to be creating instances of this class).
Implements bp board-notification
Change-Id: I2384d5e335ed9d17e29fec9a78699e3156fa225c
843b487736