Reorganize castling rights API on Board into methods named according to
conventions applied to other API.
Board::has_castling_right
Board::has_castling_right_active
Board::has_castling_right_unwrapped
These all check if a color has the right to castle on a particular side
(wing) of the board. The first takes an Option<Color>, the latter two
operate on bare Colors: the active color, or an explicit Color.
Board::grant_castling_right
Board::grant_castling_right_active
Board::grant_castling_right_unwrapped
Grant castling rights to a color. Color arguments follow the pattern above.
Board::revoke_castling_right
Board::revoke_castling_right_active
Board::revoke_castling_right_unwrapped
Revoke castling rights from a color. Color arguments follow the pattern
above.
The latter two groups of methods take a new CastleRightsOption type that
specifies either a single Wing or All.
Rework the implementation of CastleRights to take a CastleRightsOption. Update
the unit tests and make sure everything builds.
Eryn Wells
4ce7e89cdb