Services, refactor, clean up, service to automatic

Move service to automatic since it has a separate purpose.

Refactor the default.nix code to include service.nix files so it is
easier to extend code.

nixosModules/services/polkit/service.nix

@@ -0,0 +1,14 @@
+{ config, pkgs, lib, ... }:
+
+{
+  options.polkit = {
+    enable = lib.mkEnableOption "Enables polkit with kde handler";
+  };
+
+  config = lib.mkIf config.polkit.enable {
+    security.polkit.enable = true;
+    environment.systemPackages = with pkgs; [
+      polkit-kde-agent
+    ];
+  };
+}