New controls for video download/managment do not scale correctly

[radinamatic]

Summary

Different in Firefox & Chrome, evident in locales that have longer strings than English.

Probably simple to fix, needs some design/css love... 😉
@66eli77 @jtamiace

Branch or installer method

Screenshots below from 0.14 installation on XP, upgraded to 0.16 (build 177), but it's general design issue.

Screenshots

Firefox, button width not enough for string length:

Chrome, button wide enough but overlaps the container:

And while you're at it, review the media queries, because the hamburger menu does not behave well below 1000px, and main menu ends up in two rows:

[benjaoming]

Fixed in #5448, let's keep an eye out for regressions in other aspects of button rendering.