Add misc fixes

Separated from !3 (merged)

I know that you would prefer to avoid changes in translations outside the translation team. However, we need a translated description, so it could be displayed in GNOME Software. All other languages have already received this update. Besides, the po/eu.po file will be just overwritten as soon as someone updates the translation, so it doesn't hurt anyone, right?

As for Keywords in the desktop file, see c75683d0 (comment 677586)