Since he opened Posto three years ago, chef-owner Joe Cassinelli has worked to make one thing clear: This Davis Square spot isn’t “just” a pizzeria. Wood-fired pies, a centerpiece, are prepared according to the official guidelines of the Associazione Verace Pizza Napoletana, with the same ingredients and techniques used in Naples. Mozzarella is made fresh every day. Produce comes from local growers when possible. Et cetera.