code: public void addEntityListener (Family family, int priority, EntityListener listener) {
  		familyManager.addEntityListener(family, priority, listener);
  	}
docs: Adds an {@link EntityListener} for a specific {@link Family}. The listener will be notified every time an entity is
  added/removed to/from the given family. The priority determines in which order the entity listeners will be called. Lower
  value means it will get executed first.