Reviewed by GREG KING Director: Brian Henson Stars: Melissa McCarthy, Maya Rudolph, Elizabeth Banks, Joel McHale, Leslie David Baker, Cynthy Wu, Ben Falcone, voices of Bill Barretta, Dorien Davis. It probably seemed like a good idea at the time to produce a low brow, raunchy, ribald adults-only Muppets rip-off. Somewhat surprisingly the dull and largely unfunny The Happytime Murders actually comes from …