Bring It On ****
               Teenage Girl Flick Makes For Entertaining MusicalBy Isa Goldberg / Chief Theater CriticAt the top of my list of summer pop sensations is "Bring It On," the new Broadway musical which treats a trite teenage morality story with aplomb and pizzazz! With book by Jeff Whitty ("Avenue Q"), music by Tom Kitt ("Next to Normal") and Lin-Manuel Miranda ("In The Heigh…