Link the throttle control to the movement acceleration and set a minimum velocity so that the train can't stop completely.
Merge branch 'master' of github.com:V-Play/AGJ13

* 'master' of github.com:V-Play/AGJ13:
  Add performance testing section with 0 acceleration and velocit settable to the maximum.
  Added item editor.
  added basic railelements (straight and curved)
  Fix error in levelLogic with "entityId:" instead of "entityId" at assigning a custom id.