gnunet-go: ZoneMaster GUI with plugin support

[Bernd Fix]

Dear GNUnet community,

although not part of the NLnet project "GNS", I have completed a GUI for 
the ZoneMaster implementation in Golang. 
(https://git.gnunet.org/gnunet-go.git, tag v0.1.39))

The zonemaster-go unifies the Namestore, Identity and Zonemaster 
services into a single application (and database) with a HTTP GUI for 
viewing, creating, editing and deleting resource records in GNS zones. 
The base application can handle all GNS-related record types (like PKEY, 
GNS2DNS and many more) and a selected set of DNS records (A, AAAA, CNAME 
and more).

To allow the rendering and management of custom resource records defined 
by GNUnet applications like re:claimID, there is a plugin framework that 
allows to write Go- or C-based plugins that handle custom resource 
records. You find it in the repo 
https://git.gnunet.org/gnunet-go-plugins.git, tag v0.1.39). The version 
number of the plugin framework must match the version number of the 
gnunet-go code base.

This is all in a very early stage; be prepared that breaking changes 
will happen in future versions. Especially the code for C-based plugins 
will likely change - I wrote something that compiles but have never 
tested it extensively. I am not a C programmer as you can see clearly by 
reading the code. Any help to improve this is appreciated.

Cheers, Bernd.