gnunet-service, first draft in need of review.

[ng0]

Hi, I picked up the service I started working on in september.
In some parts I'm picking a starting point now with what I already
worked on in the past, file:net-misc/gnunet/files/gnunet.initd visible
at https://gnunet.org/git/youbroketheinternet-overlay.git/
specifically with the setuid parts. I'm pretty sure that the setuid
thing was removed in a later revision, but (sadly) I have to deal with
this terrible old checkout which is 0.10.1 for reasons.

I'd like someone to review the shepherd service so I can be sure that
the errors I'm getting aren't gnunet related. You have to configure a
system (didn't test VMs) with this patch. gnunet will fail to start,
and then you have to "sudo shepherd start gnunet". Your user can get
added to the now existing gnunet group, which is the upstream intended
way to use gnunet (or one of the ways) with one system user/group and
users belonging to the group to start/execute the binaries.