[ptx] hugin output formats

[Mike Runge]

>Not many applications can read the multilayer tif files created by nona,
>just gimp 2.0 and cinepaint, as far as I know.
>
>  
>
Image Magick can read and write this format as well. I tested it under 
w2k and it works fine. It is also possible to combine Multiple Tiff's to 
a single Multilayered Tiff. I tried this using convert -crop under w2k.
My intention was to crop the images before running enblend to speed up 
enblends work. My example was a 3-row-pano, which had a large 
transparent area at the bottom  There is no/little time advantage, 
because the crop also takes some time. I'm not sure if enblend is clever 
enough to use only the non-transparent areas - therefore cropping 
transparent regions maybe useless at all?!

best, mike