The Public Theater and the Onassis Foundation USA present a six performance concert of “The Gospel at Colonus” in Central Park; this gospel-infused re-telling of Sophocles’ “Oedipus at Colonus” is set at a black Pentecostal service and delivered as a sermon.  The concept is genius, the storytelling muddled, and the music a little labored. Nevertheless, it is an experience to be remembered.