完成功能如下：

（1）打印出棋盘。棋盘大小为15*15；

（2）模拟两人对弈，黑棋用字符“X”表示，白棋用“O”表示；

（3）记下对弈过程，并写入到文件中（可固定文件的名字，也可提示让游戏者自己输入一个名字）；

（4）提示读取一个之前保存的文件，并恢复到保存时的棋盘状态，并可继续对弈。-Complete the following functions:

(1) Print out the chessboard. Board size is 15* 15

(2) simulate two chess, Black with character　X　says White with　O　represents

(3) Write down the chess process and written to a file (the file name can be fixed, can also be prompted to enter a name player himself)

(4) prompt reads a previously saved file and saved back to the state board, and can continue to play chess.