Shall the San Mateo County Charter be amended to require filling of vacancies on the Board of Supervisors by election for vacancies occurring on or before October 15th of the third year of the term, and by election or appointment for vacancies after October 15th; and to authorize, for vacancies in any county elected office, and all-mailed ballot election, and commencement of the process to fill the vacancy on the date a resignation letter is filed?