I just noticed that not having this setters is specified here #144. However I do not remember that we agreed on this.
I always said, that the internal interface (e.g. IDataArray) should have only the setter with the id. But for the front facing objects an additional setter with the native type was IMO always intended. Not having this setters also conflicts with the setter schama in EntityWithMetadata where we have a setter `void metadata(const Section &metadata)`.