TRENTON — To celebrate James McGreevey's 49th birthday this week, his boyfriend threw a party for the former governor at the couple's new home in Plainfield. The idea for the 50 friends and family members who attended was to surprise McGreevey as he returned from a trip to China, where he was negotiating a deal to bring a Kean University branch to the mainland there. What a difference two years can make. It was Aug. 12, 2004, when McGreevey took his spectacular political plunge with his now-famous "I am a gay American" speech, spoken solemnly before a national television audience....