Demonstrates the use of editing methods for manipulating geometries while drawing.
                The control.insertXY method inserts a point at the given
                map coordinates (x, y) immediately prior to the most recent point
                (under the mouse).  
                The control.insertDeltaXY method inserts a point at 
                the given offset values (dx, dy) from the previously added point.
                The control.insertDirectionLength method inserts a 
                point at offset direction and length from the previously added point.
                Direction is measured counter-clockwise from the positive x-axis.
                The control.insertDeflectionLength method inserts a 
                point at offset deflection and length from the previously added point.
                Deflection is measured counter-clockwise from the previous line 
                segment.
                The control.finishSketch method completes the current
                sketch without adding the point under the user's mouse.  This 
                allows a sketch to be finished without a double-click.
                The control.cancel method discards the current 
                sketch and leaves the control active.
                The control.insertXY method may be called before 
                any points are digitized manually.  The other methods have no 
                effect until at least one point has been added to the sketch.
            
View the editing-methods.js source to see how this is done.