New version of the rom manager for PC.

Changelog:

- added: full 7z & rar support for scanner/merger/rebuilder (see docs/packer.txt for details)
- added: dir2dat optionally remove extension from setname/description
- fixed: can't close scan results window via [x] sometimes after a scan
- fixed: wrong 'unneeded fake clone:' message when creating an empty chd subfolder for fake clones