Dramatists Spring Luncheon
Bernadette Peters: Photo: Barry Gordin                    By Isa Goldberg Who was it, who just weeks ago uttered that despairing thought, "It's like I'm loosing my mind."? Appearing as herself (and not as Sally Plummer in the Broadway revival of "Follies"), Bernadette Peters was glowing at the New Dramatists 63rd Anniversary Spring Luncheon on Thursday, May…