Rotor dynamics replaced and Io global DEM added

The previous rotor dynamics didn't perform as expected so I grabbed a physics book and implemented a rotor model and integrated it into Bullet physics engine. After all there are nice numbers to display :)

I could find the most(?) complete, real global DEM for Jupiter's Io here and it has been added to Demeter after a conversion. Io has a thin atmosphere, however, I assume it has a significant amount of aerosol which is (probably) sulfur dioxide (with diameter of 1 micrometer). This produces a really colorful specular highlight at grazing angles.