hide preference [system notificaitons] entry

Change-Id: Iea05878990d8b17d8ca3d36721ca0f905205d004
tower: https://tower.im/projects/d4e0ff64158645f28d99a9ca72d0c27b/todos/208b849588024368b40d4e9b34916b41
change default size

Change-Id: Iecc20202e30f58696e5873289db013dedcdb2fc7
tower: https://tower.im/projects/d4e0ff64158645f28d99a9ca72d0c27b/todos/d696659752234ae0b763be2f4e61d550