More screen space

Ok so the lanes are getting a gameplay upgrade !

As you level up, their size will increase, giving you access to new but dangerous screen space.

Other than that : 

- The enemy spawning logic has been tweaked to be more balanced and dynamic

- You now have an option to go in and out of fullscreen

- You can go back to the title screen from the game

- Bugfix for the damage counter that did not handled properly the speed freak update

- Bugfix for the pause menu buttons that may have been slow to appear