StageTextTextEditor: calling setFocus() will put the text editor on the stage, if needed
Components Explorer: MainMenuScreen saves scroll position
List, GroupedList: selection changes are detected on validate for measurement so that they aren't lost (closes #937)
Item Renderers: added warning to documentation about disposing icons and accessories (references #942)
ComponentsExplorer, LayoutExplorer: dispose accessory and icon display objects where necessary (references #942)
ListCollection, HierarchicalCollection: data in collections may be optionally disposed (like display objects or textures) (references #942)
ComponentsExplorer, LayoutExplorer: uses new dispose() functions on collections instead of manually looping through the collections (references #942)