Save backups in the mods folder

[paoloambrosio]

When something goes wrong, many users just delete the Mods directory with all mods installed. This is very bad and it's not easy to recover from this situation. Backup (.orig) files are left around and end up replacing game files on uninstallation. The only way to restore the game state is to delete them manually.

By backing up files inside the Mods directory, we can avoid this.

Notes:

• To avoid creating directories, we can use a hash of the full path as the file name