code: protected PlaceManager createPlaceManager (PlaceConfig config)
          throws Exception
      {
          @SuppressWarnings("unchecked") Class<? extends PlaceManager> clazz =
              (Class<? extends PlaceManager>)Class.forName(config.getManagerClassName());
          return _injector.getInstance(clazz);
      }
docs: Creates an instance of a {@link PlaceManager} using the information in the supplied place
  config. Derived classes may wish to specialize this process for certain places for example
  loading user supplied place management code from a special class loader that sandboxes their
  code.