By Nidal al-Mughrabi GAZA (Reuters) – The fractious factions in the Gaza Strip and across the Israeli-occupied Palestinian territories have found one voice to unite behind – a 22-year-old youth singing songs about a lost homeland on the Middle East's version of 'American Idol'. Gaza native Mohammed Assaf has become the first Palestinian to qualify for 'Arab Idol', a TV talent show staged in Beirut, in which singers perform for judges and voting viewers. …