Added Virtual method OnWillDestory on Controller base-class

Author: jeffreylanters

Runtime/Controller.cs

@@ -104,6 +104,10 @@ public virtual void OnInitialized () { }
     /// Method invoked when the controller updates, will be called every frame.
     public virtual void OnUpdate () { }
 
+    /// Method invoked when the system will be destroyed, this will happen when
+    /// the application is closing or the controller is being destroyed.
+    public virtual void OnWillDestroy () { }
+
     // Register your systems and services to the controller. This can only be
     // done during 'OnInitialize' cycle.
     public void Register (params System.Type[] typesOf) {