Add interface-specific scores

[amjjbonvin]

Is your feature request related to a problem? Please describe.

In case of large assemblies it would be useful to be able to score the various interfaces separately. Currently we only have an overall score which might be occluding good and bad interfaces.

Describe the solution you'd like

Output the components of the score for each interface separately (either in the header of the PDB file or in a separate .score file (but this will increase the number of generated files on disk)

Possibly this should come with a new module to extra/rescore based on specified interfaces.