DESCRIPTION:

Flatten the NURB given or the current NURB, if none
given.
Mode can be one of
'-e'dge: Change position of control points that are on an
          outer edge
'-f'ace: Change position of control points that are on an
          outer face (2d/3d only)
'-i'nner: Change position of control points inside (3d only)
'-a'll: All of the above