Add pruned files to CKAN installation filters

[HebaruSan]

Hi @linuxgurugamer!

• The perma-prune button now updates the CKAN installation filters from Global install filters KSP-CKAN/CKAN#3458 if a CKAN folder is found in the game root, which will tell CKAN that it should not consider perma-pruned files as missing because the user chose to remove them. This will prevent CKAN v1.35.0 and later from prompting the user to reinstall the mods that the pruned files came from.
  Noticed thanks to @Sinomen's comments on [Feature] Ability to suppress missing file checks for user-deleted files KSP-CKAN/CKAN#4205.
• There are a bunch of seemingly unused duplicate copies of some of the files in a folder called EditorWindows. This was very confusing when I first cloned the repo; it was not clear which files were inactive and which ones I should edit until I dug into the .csproj file. I have deleted these to prevent this confusion for future developers; they can still be accessed in the git log history, if needed.

I'll probably PM you on Discord and the forum regarding this to make sure you see it. Apologies in advance for the duplication. Cheers!