This set of changes is the start of turning over to a Hash based system instead of a Rom/Dat based system. It's a long process but it will be worth it in the end.
All things that have to do with DAT mappings are in Mappings now and eveything having to do with header skippers are in Skippers now. Also, Skippers got proper implementations of matching a file to a rule and applying a rule to a file.