Export SSSOM intermediate files with information on the type of provenance, not just the provenance itself

[gaurav]

@matentzn asked for:

implement a confidence model based on SSSOM confidence that can be used to separate high confidence manually curated mappings from low confidence (less trustworthy) ones. I can help you put that together - its not too hard.

This will be harder for Babel to implement, because the intermediate files don't currently have any idea what sort of mappings are being thrown together -- but #205 will provide some of that information, so we might actually be able to start heading in this direction within a year or two.