[Feature] Display all directories not associated with a known mod

[linuxgurugamer]

Problem

Sometimes I'll install a mod by hand, a mod not known by CKAN. Then, when doing some cleanup, I may not be sure if a specific directory was installed by CKAN or not, especially when a lot of mods are installed

Suggestions

On the main CKAN screen, add a filter to show "Unknown" mod directories. This would be usable after doing at least one refresh, and it would list the unknown directories

[HebaruSan]

The suggestion isn't really viable, since the main screen and filters operate on a list of mods, not directories. This would have to be a separate, new screen.

[HebaruSan]

Duplicate of #2045