Inserts the specified Vertex entity into this Polyline entity after the specified vertex, and makes this Polyline its owner.
Returns the Object ID of the newly inserted vertex.
The Vertex will be made database resident.
If this Polyline entity is not database resident, the vertex will be made database resident when the polyline is made database resident.
To insert the specified Vertex at the start of this Polyline, use a null indexVertexId.
The Vertex entity must explicitly be closed when insertertex() returns.