UI refactoring for better mobile experience

UI changes tend to be controversial, so I won't take it personally if you hate this and reject it out of hand. I try not to take code personally anyway, but UI changes seem to merit an extra disclaimer.

The existing UI is a little frustrating for me on narrow screens, because it hides almost everything under a utility menu icon. So common actions like refresh takes an extra tap, which feels clumsy. These changes keep refresh, up, and down visible even when the rest of the navbar is hidden. That made the two tabs (about, feeds) look funny, so I pushed them onto the other side of the navbar. Finally I made the app icon act like a second refresh button, which seemed natural to me.