Update all usage of lib.concatStrings (lib.intersperse ...) to
lib.concatStringsSep. This produces the same result as per https://github.com/NixOS/nixpkgs/pull/135843,
however it yields a performance benefit on Nix versions that
support the builtins.concatStringsSep primop.
- In order to use GIO/GVFS it is enough to enable the gvfs service.
- The module option services.gvfs.package can be used to choose a
variation of the gvfs package, if desired.
All code that was at xfce4-14 has been moved to xfce/*.
Old expressions that aren't rewritten might be abandoned or broken.
Additonally I've ported the xfce4-14 thunar expression to support
thunarPlugins. We can now support this interface in the Xfce module
again, although I'm not sure if we have any plugins packaged that support
latest thunar.
