Subsurface 4.7.4 has been released

[Dirk Hohndel]

And with a small delay and a new version number, here's the release that I
promised for today.

Announcement is posted on our website (including untranslated translations
for Dutch, German, and Spanish since these are the languages we usually
get announcement translations for and since the git integration requires
those translations to exist before they get edited by the translators).

A handfull of changes, most importantly (and the trigger for doing the
release today) we once again have an AppImage. I decided not to mention
the two known issues in the AppImage. I'm kinda interesting how many
people report the problems :-)

As always, thanks to all of you for your help. Special thanks to Simon for
pushing me to get the AppImage working and his invaluable help in setting
this app on GitHub.

A special mention for the three most active contributors. Stefan and
Berthold are both new contributors this year. And of course Lubomir is one
of our top contributors with the amazing distinction that he actually
isn't a dive and does all this simply because he enjoys working on
interesting software in a welcoming community.

Statistics are very short (and my numbers are inflated by my stupidity,
err, I mean by my work as maintainer)

$ git shortlog -s -n v4.7.2..v4.7.4
    36  Dirk Hohndel
    11  Lubomir I. Ivanov
     9  Berthold Stoeger
     9  Stefan Fuchs
     8  Rick Walsh
     6  Simon Peter
     4  Jan Mulder
     1  Miika Turkia

The translators don't show up in the statistics, but they, too, deserve
our thanks for their tireless work to keep up with our changes.

Let's see how well this release will hold up. :-)

/D