They line up near the Oval Office, down the hallway toward the Cabinet Room, with their spouses and young kids in tow. When it’s their turn, the White House staffers enter for a few private moments with President Barack Obama, a photo and a farewell hug from the boss. There’s a mass exodus underway this week at the White House, as Obama and his staff pack up their offices and turn in their BlackBerrys. Some joined Obama’s team right out of college and this is the end of the only professional experience they’ve ever known. […] As White House press...