SAN FRANCISCO (Reuters) - From bondage to "breath play" and zoophilia, it's not easy keeping up with society's fast-developing sexual trends. That's why some of North America's top sexologists are hunkered down with academics and therapists at a Fisherman's Wharf hotel this weekend: to swap findings about everything from teens with underwear fetishes to transgender couples. "These couples have problems that I didn't know how to deal with," said Olga Perez Stable Cox, president of the Western U.S. region of the Society for the Scientific Study of Sexuality. "You have to understand the culture, otherwise you're an outsider, and you...