Very major changes (very WIP)

CMake fixes
Added AABB != AABB operator
Added Body::getWorld(), Body::resolve
ResolutionInfo now also returns intersection
Cell now stores all bodies
Added Grid::getX/YMin/MaxIndex()
Experimented with GridInfo performance
Added World::getBodies()
Greatly changed how Grid/GridInfo works
Created GridQuery class, that allows users to do simple
horizontal/vertical raycasting (limited but quite fast)