Improved code, added functionalities, fixed TODOs

Now boats are created without any collision
A table containing all the operations of the player has been created
Made a method to display the grid 
-> Now display the 4 grids (2 for each player) of the naval battle game
Renamed the Case class as Coordinates
The game now plays automatically and randomly
When all the boats of a player have been sunk, the game stops and tells
which player won.