Restored notifications tests.
Restored notifications tests.

This branch restores the tests previously skipped
(as a consequence of the topology refactor) in
``test_application_notifications``.

Simplified the way the number of notifications is 
tested: now, rather than checking a value in the DOM, 
we check how many model instances are present in
the notifications model list.

Also added a test for the notifications view, that was
no longer exercised due to the change described above.

R=gary.poster, benjamin.saller
CC=
https://codereview.appspot.com/6942045

mitechie/juju-gui,bac/juju-gui,jrwren/juju-gui,mitechie/juju-gui,jrwren/juju-gui,bac/juju-gui,bac/juju-gui,jrwren/juju-gui,CanonicalJS/juju-gui,mitechie/juju-gui,jrwren/juju-gui,CanonicalJS/juju-gui,mitechie/juju-gui,bac/juju-gui,CanonicalJS/juju-gui