Rewrite CSS with proper grid system

[jonashaag]

Currently the CSS is written with percentage sizes for containers and fonts (e.g. font-size: 60%, width: 72%, ...). This works well except for margin, padding, top, right, ... since they are always based on the width of the page -- even margin-top and top are calculated based on the width. Also, font-size does not change with the screen size.

Rewrite the CSS using pixels as unit for all sizes, based on a proper grid system. Maybe even some responsive one to make klaus work well with mobile/small-screen devices.