PURPOSE:   (one line only)
  Implants fake point-source images into an image of the sky.
  IMSALT will take four vectors of the same length (exten, x_pos, y_pos,
    and scale) that describe the false objects to be put in FITS images
    of real stars.  These vectors are applied in order to insert psf(s)
    of the appropriate parameters in the appropriate image(s) or extension.
    IMSALT then writes a FITS file of the same name, with the false data
    inserted.  It is important to specify the paths of the input files
    and/or the two output files, since SALTDES resists overwriting the
    original data; it will not run if the name and path of the output is
    the same as the input. 
  CCD data processing
  imname     :String, the name of the fits file to be read
  x_pos      :Vector, x locations on image
  y_pos      :Vector, y locations on image 
  mag        :Vector, magnitude of fake objects
  exten      :Vector, chooses which extensions are to contain false
              objects and how many in each. EX: exten=[1,1,7,5]
  KEYFILE   - Name of a file containing a correspondence list. This list
                 associates a set of standard names with the actual keyword
                 names found in a FITS file header. If this keyword is
                 omitted, a default list is used, as if a file with the
                 following contents had been supplied:
                  AIRMASS   K  AIRMASS
                  DATE      K  DATE-OBS
                  DATETMPL  T  DD-MM-YYYY
                  EXPDELTA  V  0.0
                  EXPTIME   K  EXPTIME
                  FILTER    K  FILTERS
                  FILENAME  K  CCDFNAME
                  OBJECT    K  OBJECT
                  UT        K  UT 
                 The middle column is a flag. It may be K, for Keyword,
                 T, for Template, or V, for Value. If it is V, the contents
                 of the third field on that line should make sense for the
                 name in the first field.

  IMDIR      :String, the path to the original images- DEFAULT:current dir
  PSFDIR     :String, the path to the psfs- DEFAULT:SRCDIR+'/psf'
  SRCDIR     :String, the path to the src and srd files- DEFAULT:''
  OUTDIR     :String, set the path for the output data file. IMSALT
              will not run if imdir=outdir - DEFAULT:'salted/'
  NOPLOTS    :Flag, if set suppresses plots of the data, the false
              data, the salted data, and the data with 'colored salt.'
  SALTFLAG   :Flag, if set this to make a note in the header that the
              file has been salted  (add keyword SALTED=T)
  QUIET      :Flag, if set will suppress chatty printed output.
  The inputs x_pos, y_pos, scale, and exten must have the same
  length.  Exten is used only with group FITS image files.

  This program requires that PSFs be pre-generated from the images (see
     PSFGEN.PRO).  The psf files must adheare to the following restrictions.
     The psfs must have the same basic format as the data files, meaning
     that they must be multi-extension if the data files are multi-extension.
     The psf header must contain the following information: 
       XCEN,YCEN - x and y location of the object on the psf
       FWHM      - fwhm of the object
       MAX       - peak pixel value of the psf
       FLUX      - flux from the psf in OBJRAD (also in psf header)
  The psf name must be the same as the filename, except with a .psf appended
     (replaces .fits tag if file name includes that).

  2004/07/14, Written by Maureen Teyssier, REU Lowell Observatory
  2004/07/15, MWB, incorporated into library.