Added callback when commands are removed

Assets/Fungus/FungusScript/Editor/SequenceEditor.cs

@@ -615,6 +615,8 @@ namespace Fungus
 				{
 					if (command == selectedCommand)
 					{
+						command.OnCommandRemoved(sequence);
+
 						Undo.RecordObject(fungusScript.selectedSequence, "Delete");
 						fungusScript.selectedSequence.commandList.RemoveAt(i);
 						Undo.DestroyObjectImmediate(command);

Assets/Fungus/FungusScript/Scripts/Command.cs

@@ -117,6 +117,12 @@ namespace Fungus
 		public virtual void OnCommandAdded(Sequence parentSequence)
 		{}
 
+		/**
+		 * Called when the command is deleted from a sequence in the editor.
+		 */
+		public virtual void OnCommandRemoved(Sequence parentSequence)
+		{}
+
 		public virtual void OnEnter()
 		{}