Comply with language attributes in HTML+RDFa

[csarven]

If lang="" or xml:lang="" is used, it is supposed to signal to the RDFa processor to not assign a language tag. However, it appears to apply the lang of the parent/document e.g.:

bibo:uri "urn:nbn:de:0074-1593-2"@en at http://ceur-ws.org/Vol-1593/

It should be bibo:uri "urn:nbn:de:0074-1593-2".