code: function _gpfAddEventListener (event, eventsHandler) {
      /*jshint validthis:true*/ // will be invoked as an object method
      var listeners = _gpfAllocateEventDispatcherListeners(this);
      if (undefined === listeners[event]) {
          listeners[event] = [];
      }
      listeners[event].push(eventsHandler);
      return this;
  }
docs: Add an event listener to the dispatcher
  
  @param {String} event name
  @param {gpf.events.Handler} eventsHandler
  @gpf:chainable