nginx: add listenAddresses

This allows the user to manually specify the addresses nginx shoud 
listen on, while still having the convinience to use the *SSL options 
and have the ports automatically applied

nixos/modules/services/web-servers/nginx/vhost-options.nix

@@ -43,9 +43,26 @@ with lib;
         IPv6 addresses must be enclosed in square brackets.
         Note: this option overrides <literal>addSSL</literal>
         and <literal>onlySSL</literal>.
+
+        If you only want to set the addresses manually and not
+        the ports, take a look at <literal>listenAddresses</literal>
       '';
     };
 
+    listenAddresses = mkOption {
+      type = with types; listOf str;
+
+      description = ''
+        Listen addresses for this virtual host.
+        Compared to <literal>listen</literal> this only sets the addreses
+        and the ports are choosen automatically.
+
+        Note: This option overrides <literal>enableIPv6</literal>
+      '';
+      default = [];
+      example = [ "127.0.0.1" "::1" ];
+    };
+
     enableACME = mkOption {
       type = types.bool;
       default = false;