REFACTORING: Multiple Roomba support ready (untested)

- All essential refactoring done IMO, but needs testing
- added roomba-selection logic to sensorUpdateTimerTimeout()
  (not sure how well it works)
- moved adding traces to scene away from mapQGraphicsView to
  IRoomba (it now has pointer to map)
- added isReady-function and variable to iRoomba. Roomba is now
  ready in safe and full modes.
- startPoints are still unmovable