HW7 part B: Advanced Graphics
Drag and drop, animation, sounds. Also fixed some bugs in the graphics and
changed tests to work with new graphics.

Use the emulator at
http://2-dot-smg-gwt-emulator.appspot.com/GwtEmulator.html ,
enter the following URL: http://2b-dot-aeroplane-chess.appspot.com
Width: 850, Height: 750