Whenever the public necessity, convenience or general welfare indicates, the Board of Commissioners may, by ordinance in accordance with the Municipalities Planning Code and the applicable laws of the Commonwealth of Pennsylvania, amend, supplement or change this chapter or the regulations, restrictions, boundaries or classifications of buildings, structures and land, as the same are established by this chapter or may hereafter be made a part hereof. The rezoning of any district or portion of any district can be accomplished only by amendment to this chapter and the Zoning Map.