#2 Option: only create new shape if not allocated previously

[Ralf Stephan]

Same problem with molecules: while cylinders may have different lengths, sphere of an element always have the same radius and material.
Nevertheless, each sphere is allocated separately. I want a button that switches on that only one sphere is created for each element, and all
others link to it. I don't know if it makes a difference in blender memory usage, but hope so.