MAJOR patch

Huge patch.

Total rework of game logic architecture. Now divided into more entities,
who each have more concrete, and less complex tasks. Together they make
a "complex" (lol ludo) solution.

Deleted the different "game type" classes such as OneVsThree etc. These
will no longer be needed.

Created:

Board.cs
BoardHelper.cs
Field.cs
PieceSet.cs
Player.cs
...and reworked GameModel.cs