The general assembly shall have the power to act in relation to the property, affairs and government of any city or town by general laws which shall apply alike to all cities and towns, but which shall not affect the form of government of any city or town. The general assembly shall also have the power to act in relation to the property, affairs and government of a particular city or town provided that such legislative action shall become effective only upon approval by a majority of the qualified electors of the said city or town voting at a general or special election, except that in the case of acts involving the imposition of a tax or the expenditure of money by a town the same shall provide for the submission thereof to those electors in said town qualified to vote upon a proposition to impose a tax or for the expenditure of money.