Tiled Gallery: Row containers to all galleries.

Circle and square galleries also have rows now, so that we can handle overflow
 when resizing for some themes more gracefully when content width changes due
 to for example a side bar in the twenty-fourteen theme.
Tiled Gallery: Group containers to all galleries.

Also square and circle galleries have groups now, so that overflow is more
graceful when for example zooming out in your browser to say 90%.