I know that this is not new code. That's the reason why I think that this discussion is out of the scope of this pull request.

Instead, I would like to point out that there is some method (like ```openquake.engine.db.models.HazardCurveDataManager.individual_*``` that could be removed too. Also, ```openquake.engine.db.models.IndividualCurveChunk``` is not used.