UPDATE 3-CIA Director Petraeus resigns, admits extra-marital affair

* Agency deputy Michael Morell leads list of replacements * Benghazi debacle had nothing to do with Patraeus' decision WASHINGTON, Nov 9 (Reuters) - CIA Director David Petraeusresigned as head of the leading U.S. spy agency on Friday,saying he had engaged in an extramarital affair andacknowledging he "showed extremely poor judgment." In a letter to the CIA workforce, Petraeus, 60, said he ...