Added reset code to bird (day 10 merge)
Added reset to grass (day 10 merge)
Fixed name onRestart -> onReset
Added reset to pipe object (day 10 merge)
Added reset to ScrollHandler object (day 10 merge)
Added get/set highscore in AssetLoader (day 10 merge)
Highscore and start screen (day 10 merge)
Fixed stuck in high score bug