Game 2: Improve display of text and images

[Magalii]

The display of the text should be improved in those ways:

• The wooden board size should match the size of the symptoms text
• The text at the end of the game should have a colored rectangle behind it to make it more readable. (That could be for example a wooden board or slightly transparent white square like for the rules.)
• The name of the STI's should be centered with respect to the ball it is written on

In order the be able to adapt the size of the board to the text, a separate image needs to be created for the wooden board.

[Magalii]

Other things to do:

• The text at the end of the game should not be displayed before final ball has finished it's move.
• The images should be displayed in front of the text when necessary (when balls move)
• The ball should be in front of the basket net when going up and behind it when it goes down. (This requires another separate image for the basket net. @guillaumereg )
• The ball should fall behind the other balls when going down.
• Change the symptom on the board only after the ball has fallen down.