GUI for epubcheck (able to search directories recursively)

This is a new GUI for IDPF’s epubcheck (see https://github.com/IDPF/epubcheck). It's freely licensed under the GNU AGPL 3 or any later version and written in Java. Downloadable packages can be found here: http://www.publishing-systems.org/downloads.php. Source code can be found here: https://github.com/publishing-systems/automated_digital_publishing/tree/master/epubcheck/epubcheck1.