plotTextString

   t = plotTextString(str,position,[delta=0.2])

 Author: ImagEval
 Purpose:
   Place a text string on a 2D graph in one of several canonical positions.
   The background of the text is set to white to make the text visible
   even if the grid is turned on

   This routine could be generalized to 3D, but it has not yet been.

   Possible positions are:  'ul','ur','ll','lr' for upper left, upper
   right, lower left, and lower right.

 Example:
  txt = 'Hello World';
  t = plotTextString(txt,'ul');