Adding support for taxonomies 6.7 and 6.8

XBRL taxonomies 6.7 and 6.8 need to be supported, including the mapping of SKR 03 accounts to DE-GAAP accounts.

The taxonomy definitions are downloadable from https://de.xbrl.org/taxonomien/taxonomie-6-7/ and https://de.xbrl.org/taxonomien/e-bilanz-hgb-taxonomie-version-6-8/

Taxonomy 6.7 is required for reports for the business year 2024. It is accepted for 2023 as an alternative to taxonomy 6.6.

Taxonomy 6.8 is required for reports for the business year 2025.