CONCORD - It is a town closely associated with history, with the environment, and with civil liberties. And Wednesday, as part of its annual town meeting, the citizens of Concord will vote on two proposals that touch on many of those ideals and would, if passed, make history. One is an environmental measure to ban the sale of water in plastic bottles that some hope will be the symbolic start to a global movement. The other is about cats. On leashes.