public override void OnInspectorGUI()
    {
        ObjectiveManager objectiveManager = target as ObjectiveManager;

        DrawDefaultInspector();
        EditorUtility.SetDirty(target);
        if (GUILayout.Button("ADD OBJECTIVE"))
        {
            Objective objective = objectiveManager.gameObject.AddComponent <Objective>();
            if (!objectiveManager.HasStarter())
            {
                objectiveManager.SetStarter(objective);
            }
        }
        EditorUtility.SetDirty(target);
    }