Reformat some unit tests
Modified the BoardStatus API

Removed the write property blackToMove.
Now use the function flipSideToMove().
Forgot a comment on the new function
Add opAssign to Board

As a result, also added opAssign to BoardStatus, Surface, and MoveList.
This change allows for a board to be copied around using the equal sign.
Like the following,

  Board a;
  Board b;
  // make changes to a
  b = a;
  // b now has the changes made to a