New "3-D" Board display window (v5.1.3.56)

[whelanh]

Under the Windows menu (or using Cntrl + 3), you can now open up a 3-D board display window.

The board is functional (you can select pieces and move: everything is coordinated with the PGN window and the main 2-D board window). You can zoom in or out using the mouse wheel or the "+" or "-" buttons. You can also flip the board. If you click and hold on an empty square, you can rotate and/or change the viewing window.