“Vision,” Margarethe von Trotta’s sympathetic imagining of the life of the 12th-century Benedictine nun Hildegard von Bingen, opens with a prologue that establishes a contemporary secular distance from the film’s devotional medieval ethos. The members of a millennialist sect anticipating their last night on earth prostrate themselves in an abbey overnight only to awaken in the bright morning sun to discover that the world hasn’t ended.