DOC: overhaul the top-level "contribute" page
Menu: attach the Doxygen node also into the documentation subdir
Menu: fix the problem with the limited IFrame height

...which caused a scrollbar to appear quite soon, when
too much sub nodes were opened. The solution is to use
a JavaScript to adjust the height of the enclosing IFrame
dynamically, based on the height of the top level document.

HTML/CSS was never able to solve that problem of dynamic
vertical space
Website: some minor tweaks and polisihng to the page layout.

especially the footer is now a real footer, moved below the
content area, spanning the whole page width. And we have a
Lumiera logo now in the Banner
Website: expand the FAQ

Yes: these are indeed frequently asked questions.
Website: clean-up
Kill the Attic

the attic used to hold the leftovers of the old website, and
the lefovers of the "ASCIIDOC day" -- mostly contents from
Cehteh's PiPaWiki, from the early days of the project.

In the last years, I've successively moved over and integrated
most substantial content. Some pages might be of historic interest
though; especially the collection of links

But since everything is preserved in the Git history, I'm removing
these pages from the hidden online presence now.