Adds support for grouped layouts outside of IE. The ListView's layout checks a few css grid related properties, and if they don't exist, switches to using flexbox in layout. The change adds the win-nocssgrid classname, includes some new rules to our stylesheets that make the win-surface element use flexbox when nocssgrid is attached, and sets up the proper flexbox flow depending on the layout orientation. The code changed inside the layout is dedicated to setting the sizes of the headerContainer+itemContainer properly, so that the flex layout can position everything as we expect