Bug#853805: unknown-horizons: Use .png icons instead of .xpm

[Jeremy Bicha]

Package: unknown-horizons
Version: 2017.1+ds-2
Tags: patch

unknown-horizons does not show up in the GNOME Software app in Ubuntu
but it does show up in Debian. This is because the appstream-generator
used by Ubuntu is a bit older and rejects all .xpm icons.

http://appstream.ubuntu.com/zesty/universe/issues/unknown-horizons.html
https://appstream.debian.org/sid/main/issues/unknown-horizons.html

The fix is pretty simple: use .png icons and do not ship a .xpm icon.
The higher resolution icons look better anyway.

I did see one difference. The .xpm has a banner that says Unknown
Horizons but the .png's don't. I think the clearer icon in an
interface like GNOME Shell's Activities Overview is more important
than that banner.

In my next email I'll attach a patch for this. There's also a patch to
drop the Debian menu because it's obsolete if your package has a
.desktop.
https://www.debian.org/doc/debian-policy/ch-opersys.html#s-menus

Thanks,
Jeremy Bicha