Also provide CRC algorithms to archive detection calls
Provide more storage for user data in the generic FileEntry class

This makes per-unpacker specific FileEntry classes obsolete
Update AFS and NIS unpackers to the new FileEntry class

...also update TODO.txt (and also add NIS PAK file unpacker)
Add skeleton for CPK unpacker

It doesn't do anything yet, needs a lot more work
Add generic object store to the FileEntry class

Maybe this should replace the other two dictionaries? But they are easier to use in most cases...
Add skeleton for ARJ unpacking

Can only identify/list archives at the moment. Needs more work :)