Remove width restriction from CSS

[humdinger]

While a width restriction makes aesthetical sense for the generated official user guide, at the translation site these limits should be lifted by changing the CSS.

When working on a translation you often have a few document windows open side by side. Those have to be arbitrarily resizeable without resulting in continuous scrolling.

min-width: 59em;
max-width: 70em;

should be removed from the style sheets used at the site.

[waddlesplash]

The entire userguide now uses a responsive-design system and will automatically adapt to any screen width.