By Nidal al-Mughrabi GAZA (Reuters) - Escalating tension between Islamist group Hamas and its Western-backed rival Fatah has pushed their "unity" government to the brink of collapse, harming efforts to rebuild the Gaza Strip and complicating Palestinian statehood ambitions. Five months after a devastating war with Israel, Gaza's residents are still occasionally jolted by explosions. But the blasts **w are more often the result of the internal conflict tearing at the fabric of Palestinian politics. ...