Fix incorrect bounds checks for SET_LAYER_INDEX reducer that caused the first item (to not be able to move down) and the last item (to not be able to move up)
Fix incorrect bounds checks for SET_LAYER_INDEX reducer that caused the first item (to not be able to move down) and the last item (to not be able to move up)

jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout,jumpinjackie/mapguide-react-layout