Switching to kde locales i/o qlocale

Open Simon Depiets requested to merge sdepiets/lokalize:master into master

This PR introduces KDE Locales instead of QLocale in the language list and in the language resolution from files.

The behavior might be different, for instance Brazil Portuguese will resolve to pt_BR language code, while before Portuguese might have been resolved to just pt. I need some help to check there is no regression, especially for languages which are defined differently in Qt and KDE (Languages of Spain, Brazilian Portuguese, Chinese variants, etc.).

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