PSR-2
Reload countries if the current locale has changed
Add CountryList::getCountriesForLanguage
PSR-2
Improve country handling

- suggest a list of countries for a specific language
- allow selecting a language without a country for locales
Merge branch 'improve-country-selection' of https://github.com/mlocati/concrete5-5.7.0 into mlocati-improve-country-selection
Merge branch 'mlocati-improve-country-selection' into develop