-added new listener callback: onChangeEntity. Callback is called when entity optional components are changed. There is no info about which components are changed (added/removed), but should be in the future).This is probably slowest callback.

source/ecs/system.d

@@ -137,6 +137,7 @@ package:
 
     void* m_add_entity;
     void* m_remove_entity;
+    void* m_change_entity;
 
     //void function(ref EntityManager.CallData data) m_initialize;
     //void function(ref EntityManager.CallData data) m_deinitilize;