review all lab sub-pages

[sonjafischbauer]

This issue will also solve the issue https://github.com/okfde/codefor.de/issues/252 - there, an automated search for / tool to remove broken links was suggested.

• check if links are still working
• check if email addresses are still working
• remove broken links as well as non-functioning email addresses

[sonjafischbauer]

Note: this can be helped with a script (does not need to be done by checking all links manually)

[sonjafischbauer]

closing this issue, as it is a near-duplicate of https://github.com/okfde/codefor.de/issues/252