adjust notification icons for network and bluetooth

- Update notification icon names

- Support notification when bluetooth device connected
  and disconnected

- Give a notification if wired cable unplugged

tower: https://tower.im/projects/1c0cd0c59ef941298c6e6b2ba6833b91/todos/f3a1bf90abf24884a781868d626caa9f/
Change-Id: I401261f824e11ef7f7ce1beac78be52585f2005d