Use KLocalizedString::setApplicationDomain, it's the correct thing for apps

Ideally one would remove -DTRANSLATION_DOMAIN= since it's mainly for libraries but in
this case there's core and console folders that even if not libraries make it harder
to remove -DTRANSLATION_DOMAIN= and make sure everything still works
so leaving the -DTRANSLATION_DOMAIN= since it doesn't hurt to have both