ADDIS ABABA (Reuters) - Former U.S. president and international poll observer Jimmy Carter urged Ethiopia's opposition parties to take their seats in parliament as he gave qualified support for the country's disputed election. The electoral board's final results from the May poll showed Prime Minister Meles Zenawi's ruling Ethiopian Peoples' Revolutionary Democratic Front and allies won enough seats in the 547-member parliament to form the next government. But the main opposition parties, the Coalition for Unity and Democracy and the United Ethiopian Democratic Forces, have alleged widespread fraud and threatened not to take their seats when the new parliament convenes...