BAGHDAD (Reuters) - The world’s largest cemetery, in Iraq’s Shi’ite holy city of Najaf, is expanding at double its usual rate as the nation’s death rate increased with the war on Islamic State. The Wadi al-Salam cemetery, Arabic for “Peace Valley,” has a special place in the hearts of Shi’ite Muslims as it surrounds the Mausoleum of their first imam, Ali Bin Abi Talib, a cousin and son-in-law of P