teiHeader consistencies

[lehkost]

• embed schema https://dracor.org/schema.rng
• TEI root element: add xml:lang="de"
• transform DLINA IDs to dracor IDs: <idno type="DLINA-ID">123</idno> → <idno type="dracor" xml:base="https://dracor.org/id/">ger000123</idno>
• wrap <docTitle> around <titlePart […]> elements
• change licence to CC0: <ab>CC0</ab><ref target="https://creativecommons.org/publicdomain/zero/1.0/">Licence</ref>
• in xml:base="https://www.wikidata.org/wiki/", change /wiki/ to /entity/