11: Major graphical changes

I haven't been posting anything for three days, that's why this update is quite huge.

1. I have added a background to the game screen. I have used assets from <wtf>https://simon-develop.itch.io/game-background-savannah</wtf>
2. I have changed fonts.  
3. I have added button images for the building buttons. Thanks for free assets, https://pauboeg.itch.io/ui-starter-pack  
4. I have implemented a ScoreBoard animation. Circular ScoreBoard fills up slowly when a player achieves the current aim value. Also, when you are in the middle of choosing a position for a new animal, your possible impact to the score is shown on the ScoreBoard.