ipad layout for header

[wbazant]

Closes #595

[ezwelty]

@wbazant Elegant solution which seems to do the trick!

Not something I suggest we tackle now, but I'll note that this sort of layout optimization gets harder with additional languages and unanticipated languages injected by browser translation tools (i.e. with a wider range of string length and text direction in a given design element) and so it can be good to think about making the existing layout(s) more robust (e.g. prevent the dropdown arrow from wrapping below the button or drop the arrow entirely, allow the top bar to grow wider for overflow, ...).