JNodes symmetry: atomization, element-to-map

Interesting user feedback (two aspects bundled in a single issue, but my weekly issue creation budget is already exhausted): Shouldn’t the following query work? ```xml <Name> <Nachname>Berger</Nachname>, <Vorname>Johann</Vorname> </Name> ``` ```xquery (: XML above as context :) (: WORKS :) 'Name: ' || string(./Name) (: FAILS :) 'Name: ' || string(element-to-map(.)/Name) ``` Observations: 1. We should have a closer look at the atomization of JNodes (concatenate leaf ·jvalue· items?) 2. The input type of `fn:element-to-map` should be extended to document nodes (in alignment with `fn:element-to-map-plan`)