Add branch generation to release job in OpenMS repo

[jpfeuffer]

I.e. in OpenMS jenkins release job trigger creation of "release/X.Y.Z" and use rules in ReadTheDocs.
So that a new version of the documentation is generated on each release.

[tapaswenipathak]

What is the documentation todo, now?

[jpfeuffer]

Someone with admin access needs to add the rules to RTDocs. And someone with access to configure Jenkins needs to edit the openms/release job to also tag/branch pyopenms-docs.
I might have done the second part but not sure if it was changed to the new name yet. Needs double checking.