Implement Hard Mode

[TheDragonMeister]

we need a button that will change the game to hard mode. hard mode is where the computer places ships in random locations on the board; no overlapping allowed. When firing, the computer will randomly shoot until it hits one of the player's ships. When it hits a ship, the computer will begin firing at nearby locations in order to find and sink that particular ship. The computer returns to firing at random locations once it has sunk that particular ship.