For Cam Thomas, this is a contract year. A huge year.  And he insists he’s not changing who he is as a player. But he’s clearly still growing into exactly whoever that’s going to be.  After failing to agree on a long-term extension with the Nets — settling for the one-year qualifying offer that suggests a possible exit from Brooklyn — Thomas has looked like a man on a mission so far this training camp and preseason.  But what exactly will that mission be?  “Cam, he has the ability to be one of