DESCTOOL
Macro: None
Function: To edit, create or read descriptor file corresponding 
to an image file.
Parameters:
1. FILE: to specify file name without suffix '.des'.
2. Every other items specified in a descriptor:
      a. Type of the image.
      b. Row number.
      c. Columns number.
      d. Minimum and maximum for each plane in the image.
      e. Average value and deviation for each plane.	
      f. Date of creation or modification of this descriptor file.
      g. Some comments concerning the image.



