Amazon said on Wednesday it would expand a marketplace that offers services from plumbing to fence repairs in 15 cities and help customers find contractors for more expensive home projects as it develops its role as a middleman for third-party vendors. The e-commerce giant said it now had more than 15 million unique services offered through its home services marketplace, up from 2 million when it launched in March. Home services are a new frontier for Amazon, pitting the company against consumer review sites Yelp Inc and Angie’s List Inc as well as U.S.