nixos/modules: Remove all usages of types.string

And replace them with a more appropriate type

Also fix up some minor module problems along the way

nixos/modules/services/web-servers/apache-httpd/per-server-options.nix

@@ -33,7 +33,7 @@ with lib;
                 description = "port to listen on";
               };
               ip = mkOption {
-                type = types.string;
+                type = types.str;
                 default = "*";
                 description = "Ip to listen on. 0.0.0.0 for ipv4 only, * for all.";
               };