OTTAWA (Reuters) - Canada's opposition Liberal Party has taken down from its website a doctored photo of Lee Harvey Oswald being shot and killed in which Conservative Prime Minister Stephen Harper's face was substituted for Oswald's. A Liberal official said on Tuesday the assassination picture, submitted as part of a photo contest in connection with the Copenhagen climate talks, should never have been there. The party on Tuesday also took down another doctored photo of Harper with his fist in a cow's posterior, which it had offered as one of the "best seven" depicting where Harper would rather be than...