Let the update.py script handle the initial, repetitive task of
packaging new plugins. With this in place, the plugin only needs to be
added to the list in `update-plugins` and most of the work will be
done automatically when the script is run. Metadata still needs to be
filled in manually and some packages may of course require additional
work/patching.
(cherry picked from commit f8096460bd15d4f13a01cfddf0a30798921fdb42)
