related_by field works for relations of RELATION_REVERSE type but not for RELATION_NORMAL type.
this does not work if related_by is used this way, it tries to call setFieldRelatedByFieldId instead of setClassNameRelatedByFieldId, and sometimes (depending on order) it uses the wrong Field, as second one override first one in relations
that does not break any functionality that were already existing, but only annoying when you want to autopopulate a relation to a class that has more than one many to one relations to the source class.
(for example, user <---author--- post and user <---validator--- post relation would cause problems)
