Entity Startup Notification.
virtual void OnStartup(void);
OnStartup is called automatically by the system if the entity is created correctly. A child class that inherits from ModaEntity can override this function to get a startup notification. In this case, the child class must call the parent's class OnStartup.
Note: The child class's constructor can be called whereas the entity is not completely created or is about to be deleted : that's why the child must wait the OnStartup notification before querying devices or doing memory allocations.