Add option to highlight unwatched items instead of watched.  

I want to easily be able to find new unwatched content; I'm not as interested in things I have watched.  

I added an option, Highlight Unwatched Instead of Watche that is disabled by default.  When enabled, it shows a star (new file, media/OverlayUnwatched.png) next to unwatched content instead of a check next to watched content, unless Hide Movie/TV Watched Status is checked.