(PDB-898) Add factset hash to replace-facts!

This commit associates a hash of each factset with the metadata of the factset
to allow us to easily tell if fact values have changed.
that stuff is in fact-data, which is the map being hashed.  I did it that way to be consistent with update-facts!, where hashing the factset object is insufficient because it doesn't contain the certname. I'll rename that variable though.