FCE FHIR Converter. Add support for translation extension

[ruscoder]

We need it for item.text, title and maybe some other fields that needs to be translated.

See example https://www.health-samurai.io/articles/multilingual-forms-global-healthcare

linkId: chief-complaint
type: string
text: Chief complaint
_text:
  translation:
    - lang: de
      content: Hauptbeschwerde
    - lang: fr
      content: Motif de consultation

Should be tranformed into:

linkId: chief-complaint
type: string
text: Chief complaint
_text:
  extension:
    - url: http://hl7.org/fhir/StructureDefinition/translation
      extension:
        - url: lang
          valueCode: de
        - url: content
          valueString: Hauptbeschwerde

    - url: http://hl7.org/fhir/StructureDefinition/translation
      extension:
        - url: lang
          valueCode: fr
        - url: content
          valueString: Motif de consultation