SANAA/ADEN (Reuters) - Separatist violence in the south loomed over a presidential election in Yemen that had just a single candidate, but Washington praised the vote ending three decades of rule by its ally Ali Abdullah Saleh. The uncontested vote anointed Abd-Rabbu Mansour Hadi - a general who served as Saleh's vice president and close confidant - as president under a deal backed by the United States, Saudi Arabia and other rich Gulf Arab states. ...