AW: Re-requesting reviews on GitHub

[Dr. Matthias St. Pierre]

> Independently of the new 'approval: *' state labelling I was wondering whether it wouldn't
> be a good idea to adopt the habit of explicitly requesting a re-review from the other reviewers
> after significant changes, using the mechanism provided by GitHub (i.e. the button with the two

To be more precise: not all reviews need to be invalidated by requesting a re-review, only the approvals.