Inserts a knot at the specified u parameter. The knot insertion doesn't modify the shape of the surface. It will add a new row of control points in the v direction and adjust the local control point's location. 

Returns eOk if successful. If the surface doesn't contain any NURBS information, returns eFail. If the surface's knot multiplicity at the u parameter is bigger than the degree in the u direction, returns eInvalidInput.

This method is implemented only for Spatial modeler and returns eNotImplementedYet status for other modelers.