WARSAW, Poland - They spent their childhoods in the rich, layered Jewish life of prewar Poland, then survived Hitler’s mission to wipe out European Jews in the ghettos and gas chambers of occupied Europe. Now, men such as Tad Taube, Sigmund Rolat and Severyn Ashkenazy, after making fortunes in the United States, have returned to Poland as philanthropists to nurture a grass-roots revival of Jewish …