How one guy carved out his niche on a social network for bridesmaid’s dresses and avocado-toast selfies — Offline, Josh Draper is a 45-year-old architect, designer and teacher at Rensselaer Polytechnic Institute who lives in Brooklyn and works at the firm PrePost. Online, Josh Draper has more than 2 million Pinterest followers — making him one of the network’s most popular men. In his Pinterest bio, he describes…