Still rather experimental implementation of fragmentation in FeOs. Works with calling the Python API of rdkit and is therefore only available in the Python interface. Some open questions:

• should this be implemented directly on the level of PcSaftParameters or rather for ChemicalRecord?
• How to store parameters (hard-coded?, passed as argument?). Somewhat obsolete if we generate ChemicalRecords first.
• How to maintain extensibility to further developments (GC-kij, Vector-GC) that would not work seemlessly with ChemicalRecords