Display the drop-down list

Unit test of

_get_english_messages() : test missing
_get_message_count() : test missing
_get_message_ids() : test missing
_get_translated_messages() : test missing
_get_translated_messages_filename() : test missing
get_message_last_proposed_translation() : test missing
get_message_translation_in_production() : test missing
get_translated_message() : test missing
get_translated_messages_filemtime() : test missing
translate() : test missing