Adjoin 2 separate layers into stereo pair

The script is useful to work on the two images of stereo pairs using the gimp, after handling the two images as separate layers during editing, this script can be used to convert two layers back into one stereo image.

This script converts two equal sized layers being positioned above each other, into one stereo image with the two former layers positioned next to each other:
1. the user choses one of two piled layers to be moved to the right of the other layer
2. the script repositions the chosen layer next to the right border of the other layer
3. the canvas is being resized to the size taken by the two layers than
4. finally the top layer is merged down

see also: http://registry.gimp.org/node/8617, my plugin to bisects a stereo image into two layers