Add AI blacklist

[GoogleFrog]

There is no standard AI blacklist system (as far as I know) so we may as well implement our own. This blacklist would be placed in a config within luaUI, probably in a folder matching the games shortname.

[gajop]

I think we should seriously consider the old validAIs.lua proposal https://springrts.com/mantis/view.php?id=2923
In the meanwhile we can just hardcode it, but I'd make this an engine/unitsync feature.

[GoogleFrog]

Can we read the internals of game archives?

[gajop]

Technically we can, but the archives (map or games) have to be specified by VFS path instead of name, which is problematic, hence first #67 needs to be resolved.
It's not hard to do, after all, it's a one-liner (https://github.com/spring/spring/blob/056449150c0e5f5f5d5dfb571fd242d75177e0f2/rts/Lua/LuaArchive.cpp#L218-L219), but it needs to be integrated well to work with pre-existing UseArchive (https://github.com/spring/spring/blob/056449150c0e5f5f5d5dfb571fd242d75177e0f2/rts/Lua/LuaVFS.cpp#L344) and MapArchive (https://github.com/spring/spring/blob/056449150c0e5f5f5d5dfb571fd242d75177e0f2/rts/Lua/LuaVFS.cpp#L383)

All in all, will be easily doable but my priorities are #7, #50 -> #100 -> #53 right now.

[gajop]

This isn't done yet really. This is just a temporary workaround until we implement validAIs.lua