Determine "state" of SoilProfileCollection before or after major modifications of site or horizon slot contents.
Two logical checks are performed on the site and horizon tables, and a third element valid returns TRUE when both checks are TRUE.
Check 1: Same number of sites in site as number of sites in horizons. No intermingling of IDs, no orphan horizons, no sites without horizons (for now)
Check 2: Site IDs match coalesced profile ID from horizons. Ensures the same relative ordering, but horizons still may be out of order within profiles