code: function Setting(settings, name, type, description, defaultValue) {
    this._settings = settings;
    this.name = name;
    this.type = type;
    this.description = description;
    this._defaultValue = defaultValue;
  
    this.onChange = util.createEvent('Setting.onChange');
    this.setDefault();
  }
docs: A class to wrap up the properties of a Setting.
  @see toolkit/components/viewconfig/content/config.js