Glencore, Vitol keep oil flowing to Greece

    By Julia Payne, Emma Farge, Dmitry Zhdannikov and Gleb Gorodyankin     Debt-stricken Greece is surviving on oil priced at a premium from trading houses Vitol and Glencore, who have stepped in as suppliers of last resort after sanctions forced Greece to halt imports from its main supplier Iran.     Greece has been forced to...