REL-2059: Fix faulty comparison of enum options in Obs objects.
REL-2059: Also deal with unweighted/unknown enums.
REL-2059: Changed comment.
REL-2059: Folded cases of no weights at all or equal weight for same/different enum types into one case.
Merge pull request #48 from fnussber/feature/REL-2059

REL-2059: Fix faulty comparison of enum options in Obs objects.