Thumbnails don't account for sub directories

[johrstrom]

Some users have been moving files around in the scenes directory. Right now, we just look in this directory for images, but there could be images in scenes/good or scenes/keep and so on.

The thumbnails may be generated correctly because it's done in the job and users would move the images after the job runs, but the link to the directory doesn't work and there are no thumbnails shown for anything in that subdirectory (even though they may exist).