Bug 862563 - Remove implicit acceptance for data reporting notification and notify on first run. r=gps

The data reporting notification was over-complicated. It wasn't
displayed for +24hr after first run and it had a weird, non-required
policy around what constituted acceptance of the policy.

The notification is now shown shortly after first startup.

The logic around "notification accepted" has been greatly simplified by
rolling it into "notification shown." Where we once were checking
whether the notification has been "accepted," we now check whether it
has been displayed. The overly complicated logic around the implicit
acceptance of the policy has also been removed.

The end result is the code for managing the state of the notification is
greatly simplified.