Hockey's most polarizing figure takes us inside the game, shedding light not only on what goes on behind closed doors, but also what makes professional athletes tick.     Sean Avery is not afraid to break the rules laid down by hockey tradition. And the most respected of these is the code of silence. For the first time, a hockey player is prepared to reveal what really goes on in the NHL, in the spirit of what Ball Four did for baseball. The money, the personalities, the adul