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.