Changed collision code, we now have several collision groups:

Changed collision code, we now have several collision groups:
  really moving objects,
  static (solid) objects,
  tilemap,
  touchable (nonsolid) objects
  (moving statics, not implemented yet will be used for moving platforms)

We now set 1 of these groups for all objects and then only check:
  moving objects vs statics + tilemap
  moving objects vs touchable objects
  moving objects vs moving objects

This gives a huge speedup for the Area42 map and will be the base for a correct fix of some collision problems encountered with ?-blocks

SVN-Revision: 2958