Move "Kexi libs" to extragear-libs, track stable i18n

They are libraries with their own release schedule, so put them
into the logical namespace extragear/libs.

The new CI system gives (correctly) less or no importance
to namespaced grouping as primary key, as it was before.

Discussed as part of D2659; this commit also include D5019.
Both review are obsoleted. It is possible to get the
translations from the 3.0 branch (as soon as I copy them...).

We can then discuss whether "move" kexi itself to extragear-office
and krita to extragear-graphics, but... not today!

CCMAIL: staniek@kde.org