Expose all fucntions of Tictactoe

We are exposing all functions of the Tictactoe module for use in
SuperTictactoe. Perhaps lately we'll do this in a separate Internal
module to adhere more closely to established tradition.
Changed all get* functions type signatures

Any function that was get(something) (such as getCols) now is more
general so that they go from any [[a]] to any [[a]]. This is so that
they can be reused in SuperTictactoe without having to resort to copy
and paste.
Made checkThreeInARow more general

Now checkThreeInARow works on any list of lists of Maybe values. This
was used so that I can reuse this function in SuperTicTactoe
Added new findWinner function

findWinner will find a winner just based on a board, indepedently of
players. This was used to simultaneously clean up code in Tictactoe and
also to be reused in Supertictactoe
Finished game over checks

Functions necessary for determining whether a supertictactoe game is
over have been finished.