HierarchicalCollection: added removeAll() function, similar to ListCollection
Tests: added some tests for GroupedList
GroupedList: fixed issues with Event.CHANGE, selectedIndex, and selectedItem after changing the data provider
List: moved selection changes triggered by data provider changes out of view port
Tests: removed unnecessary trace() call
Tests: added some tests for ProgressBar, LayoutGroup, and ScrollContainer
ScrollContainer: fixed issue where container didn't invalidate right away when a child was added or removed, meaning that calling validate() wouldn't update the layout
Tests: added some resizing tests for LayoutGroup and ScrollContainer