This extends on our model how we do releases. It introduces `NEWS.md`
as the authoritative source of our release-notes. It is pre-populated
with the release-notes from the previous 'v9' release, and contains a
suggestion for the upcoming 'v10'.
Furthermore, this adds `make release` as a simple checklist target that
contains instructions how to create a new release. Note that it is a
passive make-target which has no side-effects at all. It only prints
release information.
With this in place, we can drop `RELEASE.md`, as all information is now
combined in `make release`.
