updating folder-based plugin downloads .op file resulting in duplicate #35

If a plugin is run from a folder and has a siteid specified, the new .op file will be downloaded anyway, leaving both versions of the same plugin there. Interestingly, if I delete the .op file, the game does not download it again on the next boot. This usually happens when there is an update available, but it also often happens when it's the same exact version.

I think plugins run from folders should not be checked by the plugin manager whatsoever.