[ptx] Feature Request - image region selection mask

[Joel Young]

Joel said:
> > I also found myself doing this when I had a slightly blurry image
> > that
> > filled a gap in the panorama.  I would want the smallest possible
> > portion of that image used to build the panorama.

then Pablo said: 
> Hmm, output to a multilayer file (tif or psd) and tweak the layer
> masks.

Right.  That is what I do by hand with the gimp.  It would be very nice
to be able to do it directly in hugin.  The clipping regions are more a
property of the panorama building then of the source images so they
could/should be stored in the .pto file.