Add more langage support

[valkheim]

One big step for transform.js will be to validate that another language json can be used as a destination format. XML appears to be a good candidate.

• Add an XML based filler .See jsonFill.
• The caller might be parametrized with the lang (e.g. a function like fill(lang, ...args)). See format.
• Add some tests with a xml-based template on the example interface

See json* functions from /sources/core/utils.js.

While redesigning with a more modular approach, we should keep in mind that a user might want to define its own lang.