move all expressions to nix/; include modularized home-manager config

nix/home-manager/lib.nix

@@ -0,0 +1,22 @@
+{ 
+}:
+
+let 
+
+in {
+  mkSimpleTrayService = { execStart }: {
+    Unit = {
+      Description = "pasystray applet";
+      After = [ "graphical-session-pre.target" ];
+      PartOf = [ "graphical-session.target" ];
+    };
+
+    Install = {
+      WantedBy = [ "graphical-session.target" ];
+    };
+
+    Service = {
+      ExecStart = execStart;
+    };
+  };
+}