Added predefined locales, select via attribute

Added several (2) predefined locales. A predefined locale is chosen by
adding the "data-language" attribute to the target-input.
So far the languages english (data-language="en") and german
(data-language="de") are available.
The default fallback language if no or an invalid language-attribute is
provided is english.

Further languages can easily be added to the "locales"-object.