add comment describing world_collision_detector
add comment describing world_collision_detector

// world_collision_detector is a wrapping of
//     bbox_collision_detector<object_or_tile_identifier, 64, 3>
// to use world-style bounding-boxes rather than bbox_collision_detector-style
// bounding-boxes.

elidupree/Lasercake,Lasercake/Lasercake,idupree/Lasercake,idupree/Lasercake,elidupree/Lasercake,idupree/Lasercake,idupree/Lasercake,Lasercake/Lasercake,idupree/Lasercake,Lasercake/Lasercake,Lasercake/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,idupree/Lasercake,elidupree/Lasercake,idupree/Lasercake,elidupree/Lasercake,elidupree/Lasercake,elidupree/Lasercake