Missing imageset vs completed annotation

[Liontooth]

When the annotator encounters an empty image directory, or cannot locate the directory, or does not have access rights to the directory, it gives the same error message as when it has completed all annotations in a directory.

In addition, apache produces this error in the logs when no image is found:

[Fri Jun 17 03:18:26 2016] json_image_annotator.cgi: readline() on closed filehandle $fh at /var/www/html/annotator/json_image_annotator.cgi line 32.

Wishlist:

1. When all images have been annotated, report how many images have been annotated
2. If the image directory is empty, not accessible, or non-existent, report "No images available from $Imageset"