Make a better title screen

[LoicCK]

The title screen for now is just a simple loading screen, that the user can skip once the loading is done.

It would be better to have a proper title screen, and a loading screen that can be displayed when there is stuff loading and that it blocks the game play (ex: the user clicks start too fast on the title screen, but all the assets needed are not completely loaded by the asset manager).

• Decide on the design of the title screen
• Create a new screen - loading screen - that do the job of the current title screen
• Code the layout of the title screen using Make a better UI in-game #3