The code basically works, but there a lot of things to fix / improve.
* The alarms are stored to and read from the Shared Preferences, but there is no persistence within the app (basically they are read and stored at every access)
* The alarm list is not updated when coming back from the alarm detail view (probably related to the point above), but the actual alarm is
* The alarms preference names is sometimes built by concatenating strings, which is not really safe
* There is no check in the alarm constructor whether the stored string is a valid alarm representation
* Even though only 3 alarms can be stored on the device, we could have more in the app and let the user choose which to sync
* In the alarm detail view XML some material* drawables are used, it's possible that these break on android version < 5
* ...
A device now has a busy flag (set during synchronization). While busy,
no other communication with the device shall occur (TODO)
Refactors the non-bluetooth actions a bit #45
Next step: make use of the busy state in ControlCenter (show
a busy cursor) and in BluetoothCommunicationService (to not call other
operations while busy)
