Add a setting to only load mods stuff

[PichotM]

I have been using this for a while. Pretty useful if you work on some stuff like LC it does not load game's ymap/nodes/navmeshes/collisions so it is pretty cool!

CodeWalker is also faster for its first load if toggle on. Tested - should be working properly if my PR is complete

[PichotM]

It is a substitute to the images.meta thing but it is for me easier and better

[dexyfex]

Can you please change a few things in this before I merge it?

• Change Space.OnlyMods to public property, and set that in WorldForm.LoadSettings instead of adding the new parameter to Space.Init... Also, is Space.OnlyMods required at all? it could use the same property of the GameFileCache, but also, shouldn't all those Rpfs in Space.Init be filtered to not include mods anyway by the GameFileCache? So are any of those checks in Space necessary?
• Also maybe update GameFileCache.OnlyMods in WorldForm.LoadSettings
• Check naming convention of "checkboxMods" in SettingsForm

[dexyfex]

This was an interesting idea. but it's just too old now.. Probably the best solution for this is to try and override the appropriate files with the mods folder? But maybe this idea can be revisited if others are desperately interested in it.