[ODE] collision matrix

[Jon Watte (ODE)]

> - calculate the points on the center lines where the center lines are
> closed together.
> 
> - depending on whether those points are within or outside the
> endpoints of the cylinders, choose form the following:
> - cylinder - cylinder collision (use sum of radii)
> - cylinder - cap collision (compare nearest point of cylinder-plane
> intersect within radius)
> - cap collision - cylinder (same as above)
> - cap - cap collision (plane-plane intersect (result is a line) find
> closest point between this line and each of the two center lines, and
> again compare the distance with the radius of the cylinder)

One example:

Consider two beer cans that coincide in space. Now, move one up by a 
beer can length plus a little bit, and rotate it clockwise by 15 degrees.

The intersection will be in the middle of the second beer can, but at 
the end of the first beer can, but the proper intersection test to run 
in this case is cap/cap.