Feature/remove autotools

Finally, after 4.5 years of discussion, development and testing, we get rid of Autotools!  Thanks to Markus, Dominic and everybody who joined this journey.

The Dune website no longer uses WML, so can get rid of the Autotools. I propose to merge this branch and see what happens. There are more Autotools left-overs, we have to find and remove them. If everything goes well, we can remove Autotools from the other core modules as well.

See merge request !118