WASHINGTON - Two former presidents, a group of vets and Sen. John F. Kerry's family won coveted prime-time speaking slots at the Democratic convention yesterday, as party leaders try to define Kerry by playing up his public service and military experience. But several key Democrats did not make the initial list of speakers, including Kerry's former primary rivals Howard Dean [related, bio] and Al Sharpton. Sen. Hillary Clinton (D-N.Y.), Boston Mayor Thomas Menino - who feuded publicly with Kerry in recent weeks - and the Bay State's last presidential nominee, Michael Dukakis, also did not make the list. Even Barack...