For some reason, I *stopped* the timer if we get a push message - which
makes *no* sense. It meant that NeoChat kept running in the background
for basically no reason.
We can also make the NotificationsManager::postPushNotification function
static and avoid creating some singletons.
(cherry picked from commit 94ea1305b2)
Use the forget function to leave a room everywhere this is both for consistency and to reduce dependencies. This way no dependency on RoomManager is required to leave a room and since in all cases they have an object they can just call the function.
