Improve handling of Qt translations for Craft blueprints

At the moment it seems we miss to bundle them with our applications build via Craft.

There are multiple solutions for this, see discussion on kde-core-devel.

A hacky one to just get them for all KDE stuff would be add qttranslations as dep to ki18n for example.

I think it might make sense to decide what to do here, instead of the discussion on x lists ;=)

@vonreth @vkrause @ltoscano @aacid

If I missed people, please CC them here ;=)