PARIS (Reuters) - France's highest court upheld a conviction against oil giant Total on Tuesday over an 1999 oil spill, in a blow to the company which had hoped it would be absolved of blame for one of France's worst environmental disasters. The Cour de Cassation in Paris retained a 2008 ruling giving Total criminal responsibility over the spill of some 20,000 metric tonnes (22046 tons) of crude oil when the 24-year-old tanker Erika split apart in a storm off the northwest coast of France. ...