"for the purpose of sale or of building development": every division of a piece of land into two or more lots, parcels or parts is, of course, a subdivision. the intention is to cover all subdivision of land where the immediate or ultimate purpose is that of selling the lots or building on them. the object of inserting a definition in the text of the act is to avoid the inclusion, within the planning commission's control, of such cases as a testator's dividing his property amongst his children, partners' dividing firm property amongst themselves on dissolution, or cases of that nature.