The board of commissioners has and shall exercise all legislative powers, functions and duties conferred upon the town or its officers. It shall make all orders for the doing of work or the making or construction of any improvements, bridges or buildings. It shall levy all taxes, apportion and appropriate all funds, audit and allow all bills and accounts, payrolls and claims, and order payment thereof. It shall make all assessments for the cost of street improvements, sidewalks, sewers, and other work, improvements, or repairs which may be specially assessed. It shall make or authorize the making of all contracts and no contract shall bind or be obligatory upon the town unless either made by ordinance or resolution adopted by the board of commissioners and reduced to writing and approved by said board, or expressly authorized by ordinance or resolution adopted by the board. All heads of departments, agents and employees are the agents of the board of commissioners only, and all their acts shall be subject to review and to approval or revocation by the board of commissioners. The head of departments, superintendent, agent, employee, or officer shall from time to time, as required by law or ordinance, or when requested by the board of commissioners, or sooner if said agent shall deem it necessary for the good of the public service, report to the board of commissioners in writing respecting the business of his department, officers, or employment, all matters connected therewith. The board of commissioners may, by ordinance or resolution, assign to a head of a department, or officer, additional employment and such service shall be rendered without additional compensation. The board of commissioners shall elect and have authority over the town clerk who shall be the clerk of the board of commissioners.