Resurrection of Patchy Sphero-cylinders

[mlund]

This brings back spherocylindrical particles from Faunus version 1.

• [x] Import and refactor PSC helper functions
• [x] Bring Cigar particle up-to-date
• [x] Bring AtomData up-to-date with PSC properties
• [x] JSON I/O
• [x] Pair potentials (untested)
• [x] Resurrect test cases from Faunus v1:
  • [x] Static energy calculation
  • [x] Fibril formation
• [ ] Add Aβ42 fibril example (@SHervoe-Hansen)
• [x] Python --> VMD script. This currently has issues with hards TABs so that the python indentation is messed up
• [x] Add single frame mxyz output, see below.
• [x] Add original modifies XYZ trajectory format for visualization
• [x] Documentation