Comment 3 for bug 170981

Create two modes for the tool: Adjust and redraw.

In redraw, the new stroke should follow the mouse as if it
was a new one.

In adjust, the distance between the mouse and the old stroke
determines the amount of adjustment. Think of a magnet:
Drawing closely to the stroke will work more like redraw
while drawing farther away, it will just influence the
stroke a bit.

This should help to round forms, iron out kinks, etc.