NAME: 
  fileline
 PURPOSE:   (one line only)
  Returns one line from a file at a chosen location.
 DESCRIPTION:
 CATEGORY:
  File I/O 
 CALLING SEQUENCE:
  line=fileline(filename,linenumber)
 INPUTS:
  filename  :String, name of file to read
  linenumber:The line number of the file to read (0 indexed)
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  HEADER    : Optional header to be skipped in the file.  Default is no
                 header.  If supplied, this string (or string) array must
                 match the first N lines of the file or it will be an error.
                 The header, if provided, is not counted in the line count
                 for the line to be returned.
 OUTPUTS:
  return value is the specified line of the file (string).  If an error
    occurs, the return value is an integer value of -1.  If you get a string,
    there was no error.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  2004/07/13, Written by Maureen Teyssier, REU Lowell Observatory
  2004/07/15, MWB, incorporated into library.