add debian/ tree

[Steffen-Gr]

This is essentially (modulo build versions) what I've been using, and maintaining, to build htgettoken packages for our Hypatia cluster, it's got tested by installing and using it.
Feel free to comment, reject, improve, or merge.

[DrDaveD]

Thanks for the contribution!

Please add to the RELEASE_PROCEDURE any updates that need to be made to these files whenever there is a new version released. Ideally a script would be added to generate any changes needed so nothing needs to be updated by hand.

We will need a github action to test building. Maybe @duncanmmacleod can help with that if you don't know how to do it.

[Steffen-Gr]

Please add to the RELEASE_PROCEDURE any updates that need to be made

Will do, may take a few days. (At first glance, it's just a debchange (aka dch) run that's supposed to be done, but since the syntax is rather complex, I usually use ed's 1i mode to insert the new version section in debian/changelog. I don't know - but would like to know - how Duncan is "doing it".)