Translator: use English as fallback language. Refs #2638

If NETHGUI_DEBUG is TRUE, fallback language is not used and the label
itself is printed.
Translator: added unit tests. Refs #95
TextInput JS wiget: hide mandatory mark if field is not empty. Refs #1753

The state of the widget is updated as the user types and on view
update.
Navigation Menu: sort items alphabetically. Refs #2663