By Michael Holden and Renee Maltezou LONDON/ATHENS (Reuters) - A British museum spirited one of the world's most hotly disputed artistic masterpieces to Russia for a loan on Friday, causing an outcry in Greece, which says the priceless 2,500-year-old statue was looted from Athens and must be returned. The marble statues from the facade of the Parthenon, among the greatest works of ancient Greek ...