List, GroupedList: typical item measurement now uses an existing item renderer, if available.
List, GroupedList: reset cache on variable virtual layouts when replacing layout or data provider (closes #414). List, GroupedList, ScrollContainer: remove unncessary casts.
removed unnecessary casts
Scroller: better tracking of pending page index to allow changing page while animating.
GroupedListDataViewPort: removed unneeded casts
TileList: uses pageThrowDuration for changing pages with PageIndicator
PopUpManager: validates before centering
GroupedList: better layout caching
GroupedList: avoid null reference error for dictionaries (closes #415), added check for missing 'single' dictionary