This impulse does not cause any rotation of the kart, it just pushes
the kart orthogonal to its velocity.
2) The rotational velocity is set to 0 in case of a collision, hopefully
avoiding the problem that karts will rotate as result of a collision.
3) A collision pair now stores the exact collision point for both bodies
(which is then used to determine the side in which the impulse to be
applied).
git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/trunk@10422 178a84e3-b1eb-0310-8ba1-8eac791a3b58