Removed SwissArmyKnife. Use java.lang.Void instead
Big refactor of Collision:
- Collisions between actor and projectile are not longer executed from the perspective of projectiles (aka: for(Projectile p : projectiles) { for (Actor a : actors) { ... } }). They are now executed from the perspective of actors.
- Entities can now be looked up based on their 2D position using a simple grid. Although it uses more memory, a grid should be more performant than for example a kd tree. Combined with the previous change collisions with a lot of projectiles should be a lot faster now.
- Collision no longer has a single method with a huge amount of arguments. These have been moved to setters.
- A lot of shuffling code around in Collision which should make things much more clearer and less error prone.

Everything appears to work correctly at first glance, but there are probably a number of new bugs.