SANTA BARBARA, Calif. — The sexual abuse of a 13-year-old scout by an adult volunteer was part of a “sordid history of child sexual abuse” within the Boy Scouts that has been documented internally by the organization for nearly a century, the victim’s attorney said Monday in his opening statement at a civil trial in California. The scout, now 20, has sued the Boy Scouts of America and a local scouting council for punitive damages after being molested by a volunteer leader in 2007.