Jen Aniston and John Mayer went to their first public event together Thursday night. They joined Courteney Cox and David Arquette — who celebrated their nine-year anniversary that night — at a humanitarian event at L.A. steakhouse STK. A witness tells Usmagazine.com that Aniston and Mayer "had their arms around each other. She was rubbing his back and whispering into his ear. They were touching...