[test] Implement prototype to test StringExpression with #concat().

[Naoghuman]

[test] Implement prototype to test StringExpression with #concat().

• New enhancement to bind ObservableValues (int, long...) to a StringExpression.
• Allowed the change from an ObservableValue which will reflect then in the StringExpression.

[Naoghuman]

Should the behavior from #getMessage(...) in DefaultI18NResourceBundle replaced or extended by the new functionalities?

Old:

• Its a static injection from the arguments through MessageFormat.format(...) which returns a String.
• Locale change works.
• But if an argument is changed, then the binding must created again.

New:

• Goal is that the arguments will be injected as 'ObservableValue's.
• If an ObservableValue is changed then the String will be updated.
• The template String from the .properties file can be formated with the arguments with Bindings.format(...) or Bindings.concat(...) -> returns a StringBinding (StringExpression).
• But how do the changed in conjunction with the Locale?