Add segmentation image to thumbnail FITS images

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The shifts and orientations will be the same as those computed for creating the 
thumbnails from the DRZ image.  

Currently the shifting is done with wdrizzle, which in the case of the 
segmentation image, will create the complication that fractional drizzled 
pixels will have fractional values in the resulting seg. map.  

One way to get around this would be to use the "point" drizzle kernel but you 
get small holes in the output map where the pixels don't quite line up.

Original issue reported on code.google.com by gbrammer on 27 Sep 2010 at 3:04