Add GNOME

- Add config option to switch between window managers / desktop environments
- Remove systemPackages attribute when a service or program attribute is available
- Add GNOME to gui

system/gui/gnome.nix

@@ -0,0 +1,10 @@
+{ config, lib, pkgs, ... }:
+
+{
+  imports = [
+    ./x11.nix
+  ];
+
+  services.xserver.displayManager.gdm.enable = true;
+  services.xserver.desktopManager.gnome.enable = true;
+}