Add initial square/piece display

This commit adds a skeleton implementation for the chess-screen display
that simply displays the squares and pieces in 2D.  Displaying the
current state of the canonical board is now possible in limited
circumstances (discussed below).

The commit uses relative paths, rather than an INSTALL_ROOT to
locate texture and other files.  This means that the display code only
works in a specific directory (i.e. display/).

Additionally, the player1 color and player2 color display options
are unused, as the bmp files representing the pieces are only available
in Black and White.  This can be fixed in a future commit with the use
of transparency, and OpenGL shaders.

Finally, no board manipulation is possible via the current UI (there
is no handling for keystrokes).