Replace geom transforms with geom offsets

This replaces the usage of the geom transform class from ODE with geom offsets (see #38 (closed)). As the ODE implementation is practically the only integrated physics engine, I also removed the TransformCollider class from the interface as that simplifies the implementation a lot.

To be honest, I did not test the RosImporter or the updated SoccerBot definition as I do not have a setup ready with which I can easily test this right now. I made these changes on a best effort basis. However, I believe (and this might be wrong) that some definitions were also not quite correct before this update. If it will be in use again at some point (who knows) and there is a problem, we can still fix it at some later point.

As always, feedback is welcome :)

Closes #38 (closed)