Replaced CONTRIBUTORS.MD by CONTRIBUTORS.yaml

Now in the root of every subject, you can find only the file CONTRIBUTORS.yaml with the current contributors to the data model of the subject.

The old file CONTRIBUTORS.md is being removed.

CONTRIBUTORS.yaml is a structured format that allows automatic treatment globally across the initiative. It compiles the full name of the contributor, his/her organization, and their project and comments if necessary.

If you keep seeing it is because you are not looking at the master branch but in a specific commit (like it happens in the submodules). We update the branches in submodules daily, so tomorrow it will not appear unless you want it to go to former commits.

See one example.