5.6 and more stuff

+ 5.6 done (sound); res/bg.wav and res/game-over.wav is missing because
  the assets I used are copyrighted ("Venari Strigas" and "this is my
  despair", respectively)
+ boxes now pop out from the back instead of just appearing
+ probably more stuff
Set default blur pass count to 6

+ Looks flawless then
Fix magic self-stabilizing forces

! A box shouldn't be able to self-stabilize above the paddle center
Hide info text during Game Over screen

! The info text should not be shown during the Game Over screen;
  especially since it may show a different point count than the latter
Increase box generation with game speed

+ A fast game speed now means more boxes are created