Floor Shadows Added

Voxels immediately adjacent to the floor will create shadows using ambient occlusion.
A subtle addition that anchors the thumbnails to an imaginary floor.

To clear out the Windows Explorer Thumbnail Cache to see updated thumbnails:

1. Start a command prompt
2. Task Manager -> Select Explorer -> Right click and End Task
3. Enter this command into the command prompt started earlier:
   del %LocalAppData%\Microsoft\Windows\Explorer\thumbcache*
4. Any Access is denied errors means the old dlls are still in use. Reboot and start again.
5. Task Manager -> File -> Run new task -> explorer
6. Now you should see your new thumbnails where you have .vox files.