OCR-D GT uses wrong mods:languageTerm/@authority

[bertsky]

Throughout data_structure and data_structure_text (but not document_structure), the METS/MODS meta-data qualify the documents as:

<mods:languageTerm authority="iso639-2b" type="code">deu</mods:languageTerm>

This is clearly wrong: ISO 639-2 has two types of codes:

• B for bibliographic (language as English abbreviation, e.g. ger)
• T for terminology (language in native abbreviation, e.g. deu)