Also added interface functions to programmatically observe what is happening to the
overlays.

more than once.

use Release mode by default.

image_display widget.

the default build into a single file.

images of a different size while any kind of zoom was in effect
it could cause a segmentation fault.

jump to the beginning.

routines more robust.

first image.

the XSLT stylesheet file is always created in the same directory as the
main XML metadata file.