Added new showGameBoard function and Wall misc

As a result of trying to make showGameBoard total, I have refactored it
so that it can now be used on boards of arbitrary size instead of just
3x3 boards.

There were also other miscellaneous changes to correct warnings showing
up after -Wall. The biggest of these were providing inefficient, but
correct fallbacks for functions like getDiagonals and getCols to make
them total.
Removed showGameBoardOld

Now that the new showGameBoard has been verified to work just as the old
function did, I've removed showGameBoardOld
Added Wall flags to cabal file, fix Wall errors

Fixed some Wall warnings in Tictactoe.hs
Changed Cabal file to Wall and Werror for tests

Now tests will run with -Wall and -Werror. The Tests.hs file has had a
bunch of pragmas added so that it is exempt from some of the warnings.
Fixed Wall and Werror errors in SuperTictactoe

The biggest change made was to use the more general showBoard function
that was refactored out from showGameBoard in Tictactoe.hs for the
showSuperGameBoard function in SuperTicTacToe
Fixed Wall and Werror errors in Game.hs