This replaces the version of "generate_images.sh" that Chris created a few months ago, and to which I don't have the ability to update.
This version allows other scripts to create custom images by passing arguments to generate_notification_images.sh.
It also adds a "Restarting" image for when allsky.sh restarts (i.e., stops, then starts).  In those cases there's no need to display a "stopping" then "starting" image - just display a single "restarting".
Also added ability to have an image border.

Moving to allsky/scripts.

Actually, moved from allsky/notification_images to allsky/scripts.

The invoker (probably a Makefile) will ensure it's in the $ALLSKY_NOTIFICATION_IMAGES when it invokes this script.
Reset the formatting of the table - it's too hard to read when it's all on one line.

Put the table entries on one line, with each field separated by spaces, so it's easy to read regardless of the user's tab stop settings.