Bug 948341 - Convert Dialer to make use of the new Notification API

Usage of the new API maks the code cleaner, we only depends on
NotificationHelper for getIconURI and _checkPermissions. Since bug
890440 landed, when this new API is used there is no more hack to remove
notification, so we have to handle it ourself:
 - we have to close the notification in the 'click' event handler that
   we install
 - when we load the call log, we check for any notification and close
   them.

The second point allows us to fix correctly bug 926318.