DENVER, Colorado (AFP) – Hillary Clinton takes center stage Tuesday vowing to unite Democrats after her primary battle with Barack Obama, on the second day of the convention that will crown him as White House nominee. The former first lady will make a closely watched primetime speech, at an event which she had hoped would mark the moment when she made her own piece of history, by becoming the first woman presidential nominee. But instead, as rumors of discord between the two camps still circulate, she will urge her disgruntled followers to back Obama, ... "Let there be no mistake...