Dealer Jim Levis is devoted to amplifying the reputations of under-acknowledged talents, and that includes Elaine de Kooning, Grace Hartigan, and Hedda Stern, among others. Inaugurating his new Chelsea gallery is a fascinating, often enlightening show of paintings by de Kooning (or E de K), dating from prior to her relationship and 45-year on-and-­offish marriage to Willem de Kooning to shortly before her death in 1989.