By Geoff Robins / AFP Ford unveiled Wednesday its seventh-generation Mustang in a brash and boisterous launch event in downtown Detroit that pointed to the staying power of gasoline-powered vehicles. Ford unveiled Wednesday its seventh-generation Mustang in a brash and boisterous launch event in downtown Detroit that pointed to the staying power of gasoline-powered vehicles. The big reveal had been teased for months by company officials and organized as a celebration of the 58-year-old model. The event, organized for Ford employees and Mustang mavens, featured pulsating music, slickly produced…