This involved some restructuring:
* Themes are now split into ./Horizontal and ./Vertical sections
* DrawTiledImage() and DrawImage() work for any orientation
* Better cleanup/initializing of the (now 3D) image arrays
* Use named enums for state/side/orientation
As per usual, also includes appropriate images in the OSX theme.
Also abstracts drawing of controls to the handy _DrawImage() and
_DrawTiledImage() methods.