Finish modularising config

There are still some things I want to change, but at least there aren't two systems now.

machines/urithiru/default.nix

@@ -14,6 +14,7 @@
   environment.etc = lib.mapAttrs' (n: v: { name = "pinned-hosts/${n}"; value = { source = v.config.system.build.toplevel.outPath; }; })
     (lib.filterAttrs (n: _: n != "urithiru") nixosConfigurations);
 
+  # Machine-specific module settings
   chvp = {
     stateVersion = "20.09";
     accentor.enable = true;