mpd service: add network.{host,port} options

Closes #4084

nixos/modules/services/audio/mpd.nix

@@ -16,6 +16,10 @@ let
     sticker_file        "${cfg.dataDir}/sticker.sql"
     log_file            "syslog"
     user                "mpd"
+    ${if cfg.network.host != "any" then
+   "bind_to_address     ${cfg.network.host}" else ""}
+    ${if cfg.network.port != 6600 then
+   "port                ${cfg.network.port.toString()}" else ""}
     ${cfg.extraConfig}
   '';
 
@@ -59,6 +63,26 @@ in {
         '';
       };
 
+      network = {
+
+        host = mkOption {
+          default = "any";
+          description = ''
+            This setting sets the address for the daemon to listen on. Careful attention
+            should be paid if this is assigned to anything other then the default, any.
+            This setting can deny access to control of the daemon.
+          '';
+        };
+
+        port = mkOption {
+          default = 6600;
+          description = ''
+            This setting is the TCP port that is desired for the daemon to get assigned
+            to.
+          '';
+        };
+
+      };
     };
 
   };