Remove country and script specifications from languages

A language is only 'en', a locale is 'en_US': remove country codes from
getLanguageList so that we have only languages and not locales.

Furthermore we don't need to tell Punic which is the active locale:
Localization::changeLocale already sets the Punic default locale.
Merge pull request #1709 from mlocati/fix-getLanguageList

Remove country and script specifications from languages