Changed thumbnail size and add make_thumbs script

Merge this pull request to change the thumbnail size from 300 to 450 width and get a script that automatically generates new thumbnails.  Once you merge the request, go to http://www.jorgestradingpost.com/make_thumbs.php and press the button.  If all goes to plan, you should get a brand new thumbnail directory.  It worked well when I tested it with XAMPP.  No guarantees for how long it will take -- I only tested it with like eight images and it executed in about a full second...  As long as the script doesn't timeout (30 seconds), you'll be fine.

P.S. if the script generates a "exif_imagetype(): Read error!", that's ok.  If it generates more than one or a different error, that could be a concern.