[ODE] Collision: number of intersection points

[George Birbilis]

if it's logical to have many IDENTICAL contact points and ODE doesn't 
eliminate such somewhere in the pipeline, then hack it to create N identical 
contact points instead of a single one at such collisions

> I have a question regarding the number of points returned by 
> dCollide(....).
> - It surprises me that the collision of a sphere with a flat surface has 
> only one single point of intersection in ODE, whereas I'd assume that you 
> need several points to describe such an intersection (of circular form). 
> Can anyone tell me something about this?
> - Actually, my problem is that I do not get enough traction between wheels 
> and ground. So I thought if there were more contact points, I could create 
> more contact joints, which would then increase the traction (like having 
> wider wheels on a car increases friction). Could this be a solution or 
> does rigid body simulation work non-intuitive with respect to this 
> problem?