By Jan Wolfe WASHINGTON (Reuters) – A U.S. judge on Friday imposed a lifetime prison sentence on a member of an Islamic State militant group nicknamed “The Beatles” that beheaded American hostages, at a hearing where one victim’s mother told the defendant, “I will not hate you.” U.S. District Judge T.S. Ellis in Alexandria, Virginia, held an emotionally charged sentencing hearing for London-born Alexanda Kotey, 38, who pleaded guilty to murdering U.S. journalists James Foley and Steven Sotloff and aid workers Kayla Mueller and Peter Kassig. Hostages held by Kotey and his fellow militants nickn…