Add simple throttle control for acceleration and braking
Add the throttle control to the game scene, anchor it on gamewindowanchoritem
Merge branch 'master' of https://github.com/V-Play/AGJ13

* 'master' of https://github.com/V-Play/AGJ13:
  update obstacle generation after start init and adapt border track generation.
  change appeariance of track items.
  Add repositioning of the train.
  Add track collision signal.