code: public static void off(HammerTime hammerTime, EventType eventType, NativeHammmerHandler callback) {
  		off(hammerTime, callback, eventType.getText());
  	}
docs: Unregister hammer event.
  
  @param hammerTime {@link HammerTime} hammer gwt instance.
  @param eventType {@link org.geomajas.hammergwt.client.event.EventType}
  @param callback {@link org.geomajas.hammergwt.client.handler.NativeHammmerHandler} of the event that needs
  to be unregistered.