Document type editor cannot edit translated field names

The document type supports internationalization [1], i.e. field names can be translated in multiple languages, which are then displayed depending on then language selection of the logged editor.

However, the document type editor does not support i18n [1]. It still store fied caption in the caption property of the field node, e.g. at

/hippo:namespaces/${projectname}/${doctype}/editor:templates/_default_/${fieldname}

Steps to reproduce:

1. Create an empty project [2]
2. Add internationalization for newsdocument type following guide in [1], add # languages EN & NL.
3. Login as NL, expect to see the translated fields in Dutch.
4. Go to doc-type-editor, edit news document.

Expectation: editor can edit the Dutch field names
Actual: it only changes the "caption" property in the fieldtype node. (see screenshot)

[1] - http://www.onehippo.org/library/concepts/editor-interface/add-internationalization-i18n-to-document-types.html
[2] - http://www.onehippo.org/trails/getting-started/creating-a-project.html