Customizable Crystal Dice

Extended silvereyes customizable crystal dice SCAD code.

I added a new option: Choose between "crystal" and "prism" dice. "crystal" is the same as silvereyes dice. Further, the number of sides can be chosen freely.
The crystal requires an even number of sides. This is not enforced by the script, but an uneven number results in strange shapes. The 3-sided die does not work in crystal mode, because it does not generate a closed body.