Let WCF.MultipleLanguageInput differ between element ID and name

see [#1107]

When sending an form inside an dialog with AJAX, you probably must change the element ID to avoid conflicts with the underlying page. That's the reason why HTML differs between ID and name. Let WCF.MultipleLanguageInput do the same. 100% downward-compatible

[#1107]: https://github.com/WoltLab/WCF/issues/1107#issuecomment-13608927