Wednesday was shopping day for NJ Transit — and the airing of grievances for rail commuters who also came armed with some solutions to make their rides better. Some long-term relief for riders will be coming down the track as the commuter agency’s board of directors approved spending $178 million to buy 36 new Multilevel III rail cars. They are intended to replace some of the agency’s problematic single-level cars, that are over 40-years-old, for use during rush hour transportation to Penn Station New York. The rail car purchase is funded from the agency’s $1.679 billion capital budget, which …