By Philip Pullella VATICAN CITY (Reuters) -Pope Francis made an impassioned appeal on Sunday to Russian President Vladimir Putin to stop “this spiral of violence and death” in Ukraine, saying the crisis there was risking a nuclear escalation with uncontrollable global consequences. In an address dedicated to Ukraine and made to thousands of people in St. Peter’s Square, Francis also appealed to Ukrainian President Volodymyr Zelenskiy to be open to any “serious peace proposal”. Francis said he was making an urgent appeal “in the name of God” for an end to the conflict and said it was “absurd” t…