Value parameter of app.set() should be typed optional Object

lib/application.js

@@ -242,7 +242,7 @@ app.param = function(name, fn){
  * Mounted servers inherit their parent server's settings.
  *
  * @param {String} setting
- * @param {String} val
+ * @param {Object} [val]
  * @return {Server} for chaining
  * @api public
  */