Ballet presents a world of imaginative order, and Wednesday at the Saratoga Performing Arts Center, the New York City Ballet illuminated three different approaches to order in dance. The Twentieth Century Masters program featured the two choreographers most entwined with NYCB’s history, George Balanchine and Jerome Robbins. The evening’s third genius, modern dance’s Merce Cunningham, created works that challenged ballet’s architecture but inspired Balanchine to have NYCB dance his 1958 Summerspace, which has returned to SPAC after a fifty-five year absence.