By Nathan Layne, Gram Slattery and James Oliphant MANCHESTER, New Hampshire (Reuters) – Donald Trump and Joe Biden attacked each other on Wednesday as they prepared for a likely election rematch in November after Trump’s win in New Hampshire’s Republican presidential primary made his White House nomination increasingly likely, although his last remaining rival Nikki Haley vowed to stay in the race. Former Republican President Trump’s back-to-back wins in nominating contests put him on an almost certain path toward a general election contest with Democratic President Biden. Both turned their fi…