Make the page layouts mobile-friendly
This app was developed for a desktop use case, but people are running it on mobile devices too. Getting it in a better shape for that use case turns out to not be very hard--mostly a matter of replacing long row layouts with grid or column layouts, making graphics dynamically resize, reducing margins a bit, etc. This commit does not adapt the *content* for mobile use cases; for that, see #13. BUG: 466572 FIXED-IN: 6.0