More GitHub labels

[Dr. Matthias St. Pierre]

> Just wondering if we should have two new labels: “hold: tests needed” and “hold: documentation needed” labels?
> There are a number of PRs that come through where one or both of these are missing missing.

The two use cases you mention are actually better handled by a change request (via GitHub review) instead of a label:
A team member can formulate a change request to block the merging. Here he has more freedom to formulate what
needs to be done. This includes your two use cases, as well as the use case for the label [hold: need rebase].

The problem with it is that currently we count only approvals and don’t consider unresolved change requests
as a blocker. I think we should change that. This does not mean that a reviewer who made a change request
two months ago and lost interest is forced to re-review, only that such stale reviews must be dismissed
explicitly, if the reviewer does not respond to a re-review request within a certain time period.

Matthias