By Martyn Herman RIO DE JANEIRO, Aug 13 (Reuters) - Three days is all it took to erase any lingering doubts about Britain's domination of track cycling. At this rate they will match, or even better, the seven gold medals they won on the boards of Beijing and London. All after the year began with question marks over the form of some of the riders and continued with the resignation in April of the team's technical director Shane Sutton over allegations of sexual discrimination. More...