core.Board:
    - added withdraw method to inner class Point
core.Logic:
    - a bit of reformatting
    - added field to track whether stones should be removed
    - moveStone now checks/indicated if stone should be removed
    - moveStone now keeps track of how many stones have been played
    - moveStone now advances the game to next round if applicable
    - added method for removing stone
core.Stone:
    - added method to clean up when removing from board

test.Move:
    - now tests removing stones