Viacom employs a lot of accomplished storytellers. But few of them could dream up a drama that’s more compelling — and potentially important — than the one taking place right now at the company’s own offices in New York and Hollywood. On Friday night, Sumner Redstone — or people around him — rocked his media empire by kicking Viacom CEO Philippe Dauman and board member George Abrams off of his family trust and the board of his privately held theater chain, National…