Moved human player into Players subdirectory.
Get current player after move from new state.

Do not automatically try to compute it, which will be wrong in most
cases.
Moved getting piece's text symbol to Piece class.

Now the Piece class's ToString method does return a meaningful value.
Fixed visibility of some state methods.
Fixed using the wrong locations in jump moves.
Added random AI player.
Forbid sliding if the previous move was a capture.
Do not look multiple jumps ahead for moves.

Since a "move" now is only a single jump, and additional jumps are
represented by successive moves, when getting the available moves, do
not include double-jumps or more in the available moves.
Forbid pieces from moving if they had not jumped.

When looking for moves after a jump has happened, only look at the piece
that jumped.
Added ConsoleObserver class.
Set game as two random AIs and a console observer.