[Gchemutils-main] AppData additions required for the software center

[Richard Hughes (semi-automated)]

Hi again!

First, apologies for the direct email. I'm emailing you directly as you've been 
listed as the update contact in one or more AppData files.

We've been busy building an awesome software center, and we've been adding more 
and more metadata fields that upstream authors can set. The software center is 
now being used in Fedora, Opensuse, Ubuntu, Debian and Arch, with many millions 
of happy users.

Some of the newest features include a way to make it easy for translators to 
contribute new translations of your applications by specifying a URL in the 
gchem3d.appdata.xml gchempaint.appdata.xml gspectrum.appdata.xml 
gcrystal.appdata.xml gchemcalc.appdata.xml AppData file that tells them where 
to start looking. This can be specified by adding:

<url type="translate">http://the-web-site-with-translation-instructions/</url>

Another useful tag to add is to tell end-users where to donate, for instance:

<url type="donation">http://www.gnome.org/friends/</url>

If it's been some time since you updated the AppData file (and hey, you've got 
an app to write!) you can get add the latest metadata fields by doing 
`appstream-util upgrade gchem3d.appdata.xml gchempaint.appdata.xml 
gspectrum.appdata.xml gcrystal.appdata.xml gchemcalc.appdata.xml` and then 
replacing any FIXMEs in the file with actual data. We'll be putting more 
functionality into the software center in the future that uses this extra data, 
but we need more upstream software to opt-in before we can enable features, for 
instance, providing a button for users to donate to specific apps.

You can also use `appstream-util validate-relax` on your AppData file to check 
the various fields meet our style guidelines. If you disagree with any of the 
validation warnings, please let me know!

Of course, you don't have to do a release with these enhancements straight 
away, and if you have a stable branch it would be a good thing to backport this 
as well if it does not add translated strings or you have no string freeze 
policy.

When you've changed the file(s) and committed, please email me back and I'll 
mark your application as completed. If you don't want to hear from me ever 
again just edit the <update_contact> in the AppData file and change it to 
somebody else. I'm not planning on emailing more than once every 6 months, so 
don't worry about me spamming you with even more work to do.

Thanks,

Richard