merge TrackingWorker and CalibrationWorker into the new GazeTrackerWorker

change to state machine to always call the new worker for tracking/calibration
fix a stupid bug in the signal/slot handling
emit pointers to Mat

BrowserWindow MUST delete those mats after displaying them!
read the camera-number from the commandline
fix the unused varaible warnings
continue tracking when the user moves his head and alert a popup