replace window shutters with wall-mounted mesh node version

fixes bad rotation that was introduced with fd1e5a516a68e983300389ff9eef5bf83a071c70
(because nodeboxes can't be wallmounted, and facedir != wallmounted param2)

requires minetest from git commit dd4c21c1808acedfbcf8402c09ce9129b6ac31c7 or later.