Section 1. Cities and towns shall be bodies corporate, and, except as otherwise expressly provided, shall have the powers, exercise the privileges and be subject to the duties and liabilities provided in the several acts establishing them and in the acts relating thereto. Except as otherwise expressly provided, cities shall have all the powers of towns and such additional powers as are granted to them by their charters or by general or special law, and all laws relative to towns shall apply to cities.