The governing body of any city of the third class, except those organized under the provisions of sections 78.430 to 78.640, and any fourth class city may by ordinance provide for the employment by the governing body with the approval of the mayor of a city administrator who shall be the chief administrative assistant to the mayor and who shall have general superintending control of the administration and management of the government business, officers and employees of the city, subject to the direction and supervision of the mayor.