Rework how core lang pack is loaded for localise view

Currently editing the core language pack was completely broken because of it's custom path. And, to be honest I don't really think that it needs to be edited anyhow as the core stuff is kinda set in stone.

So after this patch if you go to the packages view only custom packages will show. However in the translations view packs are still recognized as either core, localise or 3rd party