The great playwright Tom Stoppard and his simpatico director Patrick Marber make a lasting gift of remembrance in the brilliant, gorgeous and devastating new play Leopoldstadt, opening tonight at Broadway’s Longacre Theatre. But it’s a gift that comes with strings, ropes even, the author seems to be warning us: There’s burden attached to memory, and pain, and, above all, responsibility – duty, even – that accompanies every yellowed snapshot in an old family album and every fading face that once seemed fixed with such clarity. Most of us, thankfully, won’t have the unbearably catastrophic history to carry through life that...