This summer, tourists who want attractions with a Christian flavor have at least two new options to choose from. The first, opening to the public June 5, is the Billy Graham Library, situated on 63 acres in Charlotte, N. C. For historians, the draw is the archives: the personal papers, drafts of sermons and correspondence of the man who for 60 years has been the most prominent and popular evangelist in the world. For children and families, it may be the cold milk and cookies in the caf