PieceName refactored.
Direction refactored.
PlayerStateName refactored.
PlayerState renamed to AbstractPlayerState.
HalfMove renamed to Move. There is no "FullMove" class in the program so I felt that HalfMove name is redundant.
Removed useless comment.
PieceStateName refactored.
GameSessionStateName refactored.
GameSessionStateEnd renamed to GameSessionStateGameOver.
TileColor refactored.
Player renamed to AbstractPlayer.
GamePhase refactored.
PieceState renamed to AbstractPieceState.
Fixed a few wrong names.