Add a simple implementation for steam pressure based mechanics:

- Honking decreases the pressure by 20 and therefore cows only jump if there is more than 20% pressure available
- Accelerating decreases the pressure dependent on the acceleration level (between 1 and 10)
- If there is no pressure left we can't accelerate anymore
- Breaking increased pressure more quickly (can be used for a boiler burst in the future)
- If we already have reached our minimum speed breaking won't increase the pressure anymore
- If we are traveling with a constant speed the pressure slightly increases again (so that the honk can be regenerated)
Merge branch 'master' of github.com:V-Play/AGJ13

* 'master' of github.com:V-Play/AGJ13:
  added static version of steam engine
  Anchor track to real image not to rectangle any more. Disable pooling as it works not with taking the right images yet. Create more tracks in advance because too few are created.
  adjust variation types.
  Make turnDirection of switches more visible.