By Joshua McElweeROME, April 3 (Reuters) - Pope Leo led a candle-lit service with thousands of Catholics inside Rome's famed Colosseum on Friday evening that featured prayers for war orphans and deported immigrant children, and a warning to world leaders that their decisions will be judged by God one day.The pope, who has emerged as an outspoken critic of the Iran war, listened as an evocative set of spiritual meditations was read aloud inside the ancient amphitheatre to observe Good Friday, the...