Disconnect prefab instance when creating Flowcharts

If Flowchart is a prefab instance then the properties for every command
are displayed in bold. There’s no real benefit to preserving the prefab
instance so easiest thing is to just break the instance link.

Assets/Fungus/Flowchart/Editor/FlowchartMenuItems.cs

@@ -23,6 +23,7 @@ namespace Fungus
 			}
 
 			GameObject go = PrefabUtility.InstantiatePrefab(prefab) as GameObject;
+			PrefabUtility.DisconnectPrefabInstance(go);
 
 			Camera sceneCam = SceneView.currentDrawingSceneView.camera;