EXCLUSIVE: Paul Shaffer has signed with Don Buchwald & Associates in all areas, with plans to branch out into creating his own television opportunities. David Letterman’s longtime musical director, bandleader and comic foil, Shaffer recently appeared in Bill Murray’s Netflix special A Very Murray Christmas directed by Sofia Coppola. DBA says it is working to develop a program around Shaffer’s diversified talents and will continue to field opportunities in acting, hosting…