For more than 100 years, the adventures of Peter Pan have captivated audiences, from the famous play starring Mary Martin in the title role to the beloved Disney movie. The classic tale was the brainchild of playwright J.M. Barrie. Now, the story of how Barrie came to imagine a world of fairies and lost boys is the basis of a new musical, based on the 2004 film “Finding Neverland,” as WGBH Arts Editor Jared Bowen explained.