This table's export and import weren't working:
1. It didn't have a Config in export.py, so it wasn't exported at all.
2. Its `date_created` wasn't registered in `DATE_FIELDS`.
3. It wasn't registered in `ID_MAPS` in import_realm.py, so having any
SavedSnippets in the export would cause the import to fail with an
exception.
4. It was missing a `fix_datetime_fields` call in its import codepath.