added cases for VatNumber property into LoadFromJSON and LoadFromNode private methods
added cases for VatNumber property into LoadFromJSON and LoadFromNode private methods

hewittj/chargify-dot-net,hewittj/chargify-dot-net,kfrancis/chargify-dot-net,kfrancis/chargify-dot-net,kfrancis/chargify-dot-net,hewittj/chargify-dot-net