[ptx] New hugin tutorial - Stitching flat scanned images

[Marek Januszewski]

Hello,

  I decreased the fov to 25 and it went fine now (almost perfect).
I think this tutorial should stay as is for the most part, but 
definitely needs some followup or advanced section after the end of 
current text. One topic that should be covered is making it straight 
through horizontal line and image 0 r optimization. Maybe also setting 
the anchor spot for centering.

  Anyway it's a great start

--
thanks,
Marek