The selectmen of a town, when they deem it necessary, may appoint special police officers who shall continue in office during the pleasure of the selectmen, or until their successors are chosen or appointed. The selectmen may designate one of the police officers as chief of police or superintendent and as such officer the chief of police or superintendent shall exercise authority over and supervise or superintend other police officers, watchmen, or constables appointed under the provisions of this chapter, and said police officers, watchmen, or constables shall be accountable and responsible to said chief of police or superintendent. The designation as chief of police by the selectmen may be in the form of a contract specifying that the authority of the designee ceases on the date stated in the contract, regardless of whether a successor has been designated. Nothing herein shall be construed to preclude or prevent a town from electing constables or police officers at an annual town meeting pursuant to the provisions of N.H. Rev. Stat. § 41:47.