Dye branch: handling symmetry

[BvB93]

Find a way to handle symmetry equivalent configurations.

Option A: Manually mark symmetry equivalent positions. After the dyes have been generated, delete all symmetry equivalent structures based on these patterns in these user-specified positions.
Option B: Find a package which can automatically recognize symmetry, removing the need for manual interference.

[BvB93]

Option C: Hybrid between option A & B: manually specifiy the point group, automatically find all symmetry equivalent positions.

[BvB93]

Added the find_equivalent_atoms() function, which finds and returns the indices of symmetry equivalent atoms. @JBelic: A potential (start of a) solution for the symmetry problem?

[JBelic]

Cool. I saw it. It's a good start, I'll make a little change with focus on molecules.