VATICAN CITY (Reuters) - Pope Benedict said in a historic announcement he no longer had the mental and physical strength to run the Roman Catholic Church and would become the first pontiff in more than 700 years to resign, leaving his inner circle "incredulous". Church officials tried to relay a climate of calm confidence in the running of a 2,000-year-old institution but the decision could lead to one of the most uncertain and unstable periods in centuries for a Church besieged by scandal and defections. ...