DOC: Update and extend importance and inheritance

.gitignore

CHANGELOG.md

src/doc/Data-Model.md

src/doc/_static/css/server_docu.css

src/doc/conf.py

src/doc/specification/AbstractProperty.md

src/doc/specification/RecordType.md

src/doc/specification/RecordType.rst

src/main/java/org/caosdb/server/entity/StatementStatus.java