Add Wyckoff positions for atoms

[rozyczko]

We need to add Wyckoff symbol + multiplicity to the Site attributes display in the library,
This should be based preferably on the Wyckoff evaluation in EasyCrystallography ( easyscience/EasyCrystallography#84 ) but can temporarily be done using cryspy.

We currently do it in the App, so the code needs to be moved here.