This file concerns material implementation in the simulator.

Terminology:
Since "Material" is used for OpenGL stuff and also in OSG 
 we should use something else for the physical material: substance

So how to implement substance to cover all collission cases and requirements.
It would be nice to keep the collisioncontrol as it is for compatibility reasons.
In general:

- every ode geom should get a user data pointer to the primitive 
- primitive has a certain substance 
- 2 substance define collision parameters
- also an optional callback function for user defined handling
- collission detection is done globally. 
- via joint connected geoms are stored in a set (globally)
- spaces are globally registered


