Add functions for calculating affinity matrix (both SOAP and FSC)

[jolaem]

These were so far created in separate scripts. Probably shouldn't be fully integrated with the training routines, but it would be good to add them in utils or somewhere similar so that users can crate them for their data (even if they might want to use another similarity function, for proteins FSC will always be useful).

[marjanfamili]

This should be in tools