Importer: Sanitize UUIDs

Closes #3844
- Before importing, all data is checked for incorrect UUIDs. If check
fails, data is sanitized and outfitted with correct UUIDS.
- Scaffolding allows for easy implementation of additional
sanitization, should that be required in the future.
- Test included, old tests updated.
Merge pull request #3855 from felixrieseberg/iss3844-importer

Importer: Sanitize UUIDs