Implement another level + main menu

[tbrebant]

It would be cool to:

• have one more level
• a main menu to choose the level
• after victory or game over, the game will switch back to the main menu
• add an exit button in levels to go back to the main menu

[ronkorving]

Would it be possible to split this up into multiple issues? (some things are inherently linked, one cannot exist without the other, but perhaps that's not the case for some of these?)

[tbrebant]

The "main" issue is creating a new level.
The UI part is very easy to do, not worth to create a specific issue I think.