SERIES PREMIERE: I’m not recommending this, necessarily, but it’s certainly worth noting, as television’s first reality-series musical of sorts. It takes place in Branson, MO, the place where show-biz performers past their prime come to perform for aging, enthusiastic audiences. And it concerns the Baldknobbers Jamboree, the unfortunately named family revue that has operated in Branson for 55 years. That’s an astounding feat of show-business longevity, but understandably,