Special handling for Chinese: Mapping to unlocalized

Adding special handling to the Chinese translations. Wenn encountering some localized UI languages for which we do not have dedicated translations, map them to the Simple or Traditional Chinese variants first to try finding a suitable translation before going into "guess- mode". This should yield more predictable and sane results.

Special handling is required due to the unlocalized variants have an unusual language code (e.g. zh-Hans instead of just zh) and hence the previous code would not correctly use these generic translations.

Closes #511 (closed)