Bug 920414 - [Dialer][User Story] Show "call ended" message at the end of calls.

Important changes on this bug:
- Removed `CallScreen.singleLine` and add `CallScreen.updateSingleLine()`. Since all calls have 2 seconds of transitions after hanging up, it's now required to let `CallScreen` query remaining visible calls at certain time to inform `CallScreen` update its `single-line` style. The style is determined by `CallScreen` itself by doing query select so no parameter is needed now.