Fix for cursor problem in samples/simple-editor.rb

samples/simple-editor.rb seemed to show an off-by-one the cursor.  In fact, the
cursor was positioned right, but just lagging on redraws (i.e. cursor moved
after drawing for it had already been done)

We update position only as needed and lean on RedrawingAspect for redraws.
Renaming from redraw -> move to be more descriptive
Merge pull request #554 from shoes/stale_textcursor

Fix for cursor problem in samples/simple-editor.rb