Fixed Coin3D units hanling. Removed implicit assumption that all models are...

Fixed Coin3D units hanling. Removed implicit assumption that all models are given in millimeters. Now all Coin3D related models may have a units tag or if not, the units are assumed as meters (standard in Coin). This change does only affect the model import/export, since all Simox internal computations are still performed in millimeters.
Added unit tags to 3d model files and fixed all demos and examples.

git-svn-id: http://svn.code.sf.net/p/simox/code/trunk@328 042f3d55-54a8-47e9-b7fb-15903f145c44