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
I don't think it's necessary to export only for testing, so I require the testing file in suitesetup. The reason why I didn't put this part in setup is because required script will only runs once, so the stub handler will not be called at second time.