PHILADELPHIA — Bernie Sanders called his campaign a “fantastic start” to a movement to revolutionize politics and policy, but as the Democratic National Convention got underway, his supporters had mixed feelings about his call for party unity.In fact, the Vermont Democratic socialist was booed Monday when he told a throng of supporters in Philadelphia “we’ve got to elect Hillary Clinton and Tim Kaine,” her running mate.Not everyone was booing.“He’s a team player even if it’s for that team played dirty against him,” said Sanders delegate Brent Oleson of Marion.