§ 119-m. Legislative intent. The provisions of this article are designed to effectuate in part (1) section two-a of article eight of the constitution and (2) section one of article eight of the constitution as amended January first, nineteen hundred sixty, and shall be in addition to and not in substitution for or in limitation of any other authorization for performance by municipal corporations or districts of their functions, powers or duties on a cooperative, joint or contract basis.