LONDON (Reuters) - European shares fell and the dollar firmed on Monday as low-risk assets gained at the start of a week in which the United States elects a new president and Greece faces a make-or-break parliamentary vote. The FTSEurofirst index of top European shares opened down 0.4 percent after ending the previous week at a two-week high. London's FTSE 100 was down 0.4 percent, Paris's CAC-40 was down 0.7 and Frankfurt's DAX was down 0.6 percent. "You don't want to have too much risk ahead of the U.S. ...