As a developer I would like to manipulate values of fields property in the contentCreateStruct structure

Implemented getter and setter methods for the fields property of contenCreateStruct structure.
By making these changes I'm able to create a new content and update its fields using JS Rest Client.
https://jira.ez.no/browse/EZP-23276
my previous comment is hidden due a code change, the question is still pending:
> I'm unsure about that?
> @pspanja @andrerom @bdunogier is it possible to have a content create struct in a language with some field in another one ?