WASHINGTON(Reuters) - Shi’ite militias in Iraq detained, tortured and abused far more Sunni civilians during the American-backed capture of the town of Falluja in June than U.S. officials have publicly acknowledged, Reuters has found. An Iraqi Shi'ite fighter fires artillery during clashes with Islamic State militants near Falluja, Iraq, May 29, 2016. REUTERS/Staff/File Photo More than 700 Sunni m