EMI: Separate radius and center for mesh collision sphere
EMI/GRIM: Implement collision handling for EMI

- for solving the Monkey Kombat puzzle it is necessary that a kombat is
  triggered when Guybrush runs into one of the monkeys on the map
- implement SetActorCollisionMode and SetActorCollisionScale
- add EMI-specific calculations for retrieving the sphere data for the
  actors (and some minor refactoring for better readability)

The following changes may alter the behaviour in GRIM, too:
- in Actor::collisionHandlerCallback(), call the collision handler for
  both affected objects (that is necessary since only one actor may have
  a collision handler associated in lua but it may happen that the
  character with the handler is standing still and the other one is run
  into him)
- Actor::handleCollisionTo() did only update a given position to ensure
  that there is no collision - so it is necessary to actually check for
  collisions and execute the lua callback if necessary (via
  Actor::handleCollisionWith())
Merge pull request #797 from chkr-private/collision-fixes

Collision fixes