Improve handling of labels

Each data item (that's what we call a single array entry) can have a #label string (e.g. Body, Title) and a #parent_label array (important when e.g. having multiple values in fields, multiple nodes in one job or when using summaries (e.g. Node A > Body > Summery).

Right now, you're only passing the key forward, as far as I can see. That means that translators will see only see a technical identifier of the string that should be translated (e.g. "5]body][0][value"), which isn't very helpful.

You might want to pass that information through to your site somehow, *if* you are capable of handling it.