Android: QBluetoothDeviceDiscoveryAgent implementation

Change-Id: I41e11da3e623c6c1a960c6feb0ba626f26b0a18a
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Android: Use new logging category for Android specific debug/warnings

Change-Id: I5aaa4050fd30da70b63bfcb0e5ba33b43289c7f9
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>