Density calculations for non-spherical objects about celestia

[375gnu]

We have Density parameter.

[ajtribick]

Yes, makes sense to add this calculation. Probably won't be able to do anything reasonable for objects with meshes for the time being, so would skip the density calculation for those.

[JiliTheSpaceboy]

Yes, makes sense to add this calculation. Probably won't be able to do anything reasonable for objects with meshes for the time being, so would skip the density calculation for those.

Some objects with meshes, like Ceres and Mimas, are close enough to ellipsoidal shape that their calculations wouldn't be significantly off, though maybe we can instead simply add manual density input for these cases?