Most of New Jersey’s beaches will start the summer in decent shape after a winter of storms, but significant erosion remains a problem in several spots. Even in shore towns where erosion has not reached crisis levels, the shoreline is somewhat narrower this year. On some beaches where there could be less room for everyone, local officials are banning tents, cabanas and other sheltering devices that take up an inordinate amount of space. And swimmers should watch out for possible strong rip currents this summer, as officials warn that eroded sand has gathered offshore in several sandbars along …