ScrollContainer: now uses a subclass of LayoutGroup for its view port to avoid having so much duplicate code
TextFieldTextEditor: removed unnecessary call to fillRect() that was needed when reusing bitmap data in old versions
Examples: if using ScreenNavigator in drawers on a tablet, clip the ScreenNavigator's content so that transitions don't bleed outside
TextFieldTextRenderer: support for multiple textures, increasing the maximum bounds beyond 2048 (references #255)