DefaultFocusManager: fix for issue where old focus didn't dispatch a proper FOCUS_OUT event when removed from stage (references #908)
DefaultFocusManager: dispatches FOCUS_OUT event to old focus after the _focus variable is changed so that the focus getter can be called in the listener
PickerList: implements IFocusDisplayObject and handles passing focus to the button or list better (closes #908)
List, GroupedList: item renderers are updated (like updateItemAt()) when dataProvider is replaced or dataProvider dispatches CollectionEventType.RESET (closes #909)