[US-03] Ship damage, announcing sunk, and finishing

As a player I need the game to follow the damage of ships and recognize when everything is destroyed, so that the outcome becomes clear.

The program should count how many parts of each ship are hit and know when a ship has all of its parts damaged. Then it should tell the player that the ship is sunk. When all ships of one participant are gone, the system should declare that the other player has won and block any more inputs. It should also allow starting over through something like a New Game option.

Acceptance ideas: – When the last healthy square of a ship gets hit, that ship should be indicated as sunk. – When the final enemy ship is destroyed, the game should end, show who won, and not allow further shooting. – When a finished game is restarted, both boards become empty and hidden again.