Fixed a race condition between ACTION_DEVICE_CHANGED event handlers:
- DeviceCommunicationService added the device to the database
- DeviceManager notified the views to be refreshed
When the latter happened before the former, thew new device would not
be displayed.
=> Let DeviceManager do both.
Basically moved code out of ControlCenter to a separate class. Also provides
change events when the device list has changed, or changes to the device
state have occurred.
cpfeiffer