Game 2: Fix exit of game

[Magalii]

At the end of the game, their is no button to go to the next game, nor to leave the game. The only thing possible is to use the general "go back" button on the phone. Then if we go back we end up on the starter screen of game 3 before reaching the menu.
We need to:

• Add a "continue" button to go to game 3 if the game was won
• Add "retry" and "exit" buttons if the game is lost
• Fix the way the go back button works so it leads to the menu and not the game 3