NIGHT AT THE OPERA Great Score Overcomes Bland ‘Sweeney’ Setting By PAT THORPE • Review for www.AllOTSEGO.com COOPERSTOWN – Stephen Sondheim’s “Sweeney Todd” has been described as “operatic” since its debut in 1979 and it didn’t take long for this musical thriller to move to the opera house. John DeMain conducted Sweeney’s operatic debut in 1984 and has probably led more performances than anyone on Earth – very good reasons the Glimmerglass Festival orchestra sails with confidence and power through…