[ODE] Box-mesh collision

[Marco Grubert]

One thing about the Box-Tri collider I noticed is that it assumes the normal
to be that of the triangle. This works fine for a box falling onto a
triangle, but yields wrong results for a triangle falling onto a box. I am
currently working on the tri-tri detection and pick the normal based on
which object is moving and which one is static. This avoids some explosions
but introduces other instabilities..

- Marco Grubert