get rid of the MM directory or make it a subdirectory of something meaningful

[bansp]

The MM directory contains the mind-map source and a graphic snapshot of an early version of format family trees. I am not at all sure if it is useful still. It has to be cloned by whoever clones/forks the SIS to do work on it, and it prooobably doesn't give us extra points in the professional-look section.

BUT it might make sense to keep a root subdirectory, where we could perhaps store and maintain the OpenAPI definition of our API instance. Then, IF the mind map were deemed useful, it could still be part of the tree.

Third thought: the OpenAPI description goes into our generated pages... I.e., since we don't want to open a second repo under clarin-eric, it would go into https://github.com/IDS-Mannheim/IDS-Mannheim.github.io

And this is how a task issue has turned into a discussion issue... let me add the label...