ccdproc: this version for processing flat field frames

       images = @flats.lis      List of CCD images to correct
      (output = "")             List of output CCD images
     (ccdtype = "")             CCD image type to correct
   (max_cache = 0)              Maximum image caching memory (in Mbytes)
      (noproc = no)             List processing steps only?\n
      (fixpix = no)             Fix bad CCD lines and columns?
    (overscan = yes) <=         Apply overscan strip correction?
        (trim = yes) <=         Trim the image?
     (zerocor = yes) <=         Apply zero level correction?
     (darkcor = no)             Apply dark count correction?
     (flatcor = no)  <=         Apply flat field correction?
    (illumcor = no)             Apply illumination correction?
   (fringecor = no)             Apply fringe correction?
     (readcor = no)             Convert zero level image to readout correction?
     (scancor = no)             Convert flat field image to scan correction?\n
    (readaxis = "line")         Read out axis (column|line)
     (fixfile = "/astro/users/ben/premap/calibration/badpix_APO_DIS.dat")   File describing the bad lines and columns
     (biassec = image header)   Overscan strip image section
     (trimsec = different for red and blue!)   Trim data section
        (zero = bias.imh)       Zero level calibration image
        (dark = "")             Dark count calibration image
        (flat = bf.imh)         Flat field images
       (illum = "")             Illumination correction images
      (fringe = "")             Fringe correction images
  (minreplace = 0.)             Minimum flat field value
    (scantype = "shortscan")    Scan type (shortscan|longscan)
       (nscan = 1)              Number of short scan lines\n
 (interactive = no)             Fit overscan interactively?
    (function = "legendre")     Fitting function
       (order = 1)              Number of polynomial terms or spline pieces
      (sample = "*")            Sample points to fit
    (naverage = 1)              Number of sample points to combine
    (niterate = 1)              Number of rejection iterations
  (low_reject = 3.)             Low sigma rejection factor
 (high_reject = 3.)             High sigma rejection factor
        (grow = 0.)             Rejection growing radius
        (mode = "ql")