Update CONTRIBUTING.md
Translated using Weblate (Russian)

Currently translated at 93.3% (755 of 809 strings)
Update i18n documentation headers

copy_pofiles is no more with the Weblate migration.
Translated using Weblate (Danish)

Currently translated at 63.7% (515 of 809 strings)
Translated using Weblate (Russian)

Currently translated at 96.2% (778 of 809 strings)
Do not display empty helptext in tabwidget
Correct misleading comment
Shift down tabwidget by 2px

There is enough space and the minimap panel background image fits as
well, so why not try this for a bit.
Merge branch 'master' into tabwidget