JUBA (Reuters) - U.S. Secretary of State Hillary Clinton urged South Sudan and Sudan on Friday to end an oil dispute that has brought the neighbors to the brink of war, during the highest-level visit of a U.S. official to Juba since its independence a year ago. Clinton began her first visit to Africa's newest nation just hours after a U.N. Security Council deadline expired for the neighbors to solve a long list of disputes ranging from border security to oil payments. ...