All of the templates include a link to the Roundup docs.

I am watching the stats for that including the referer header. I see
entries from private ip address space with port 8080, 8917 etc. This is obviously
clicking on the link on a tracker.

I would like to not see the referer but get info on the version of Roundup being run.
A change to the Roundup docs link like:

   <a
    tal:attributes="href python:'https://www.roundup-tracker.org?ref=from_roundup-' +
                    utils.roundup_version()" 
        referrerpolicy="no-referrer" i18n:translate="">Roundup docs</a>

where utils.roundup_version is a new TemplatingUtils method. Add to cgi/templating.py and it 
returns a string like "2.3.0". This should be done on all templates.

My implementation of roundup_version was added as templating util extension. The code is:

    from roundup import __version__ as roundup_version_str
    def roundup_version():
        return roundup_version_str

    def init(tracker):
        tracker.registerUtil('roundup_version', roundup_version)

when added to templating.py, probably only need the first three lines.

In addition to code change, add two sections to doc/upgrading.txt. Make adding
the referrerpolicy recommended and changing to a new url with the ref optional.

Hopefully this will get some info on what versions are in the wild and stop
internal url's from escaping to the logs.