Building minimax w/ chance node

[nivram108]

play.cpp

• [x] Recover one game step
• [x] Control the game in a contest mode. ( We can assign the dice directly. the opponent choose a movement directly. )

ewnAI.cpp

• [x] Create a table for available moves 傳入<dice, chesses_exist>，得到<available_chess, available_chess>
• [x] miniMax: Get best value for each move for a chess, sum the possible chess' value.
• [x] bug: AI didn't select the assigned chess

[tyhsu]

我修改了issue的內容喔 / 然後recover這個位置 為什麼不乾脆先判有沒有輸入z再決定要不要update board 這樣根本不需要複製Game什麼的啊＠＠