Added Video Thumbnail

Ok.. I've added a video thumbnail which is ripped from the Thumbs.db file in the windows directory. I've been looking at a nice clean way of implementing a thumb from a video file in the event that thumbs.db doesn't have it, and should have something by next week.

I'm debating about adding support for thumbs with pdf, Microsoft based files (excel, word, etc.) and maybe a few other formats, but am yet convinced to put in the effort. Let me know if the application needs anything more, I'm willing to consider it.