Popup lib: Added duration property to ZoomAndFadeBehavior, added null check to stage in KeepCenteredBehavior, added ZoomAndFadeBehavior using Spark effects, name changes: ZoomAndFadePopUpBehavior > ZoomAndFadeBehavior, KeepCenteredBehaviour > KeepCenteredBehavior, CenterPopUpBehavior > CenterBehavior, added more feature combinations to samples.
