Improve scaling of pictures in side-by-side arrangements

• Adapt CSS to remove left-right alternation of images on tablets. Pages hifisfor/rse etc. need an adaptation of the CSS. On tablets the left-right alternation of images is removed to have more space for text on small tablet screens.
• Remove CSS customisations on page hifisfor/scientists. Page CSS is streamlined with other pages like hifisfor/rse etc.
• Page media need different structure and own CSS.

Closes #342 (closed)