Moved the code that stops the RingService on the call being answered from the CallAlertBroadcastReceiver to the RingService
Modified the way that call alert data is stored, so that it's easy to add as many alerts as the user wants. Also, modified the display of call alerts so that it looks prettier and can be repeated. It's not all linked together yet, however, so the UI is currently broken. Not all tested yet thorougly, either.