Bug 1051793 - [CMAS] Plug in real CMAS input to the CMAS application

- Add cellbroadcast system message handler
- Removed unused styling and testing UI
- Add localization properties
Sorry I forgot to add comment about this: The previous patch simply use the notification's title for showing the attention screen, but it should be localized anyway so I set the title ID in icon imageURL instead. Not sure it's proper way to use notification, but I have no better idea how to saving more data in notification :-/