"Super Hexagon" Upgrades & a couple fixes

- Switched to live time rather than kill score/multiplier for game score
(use "World.getPlayerLiveTime()" to get the current run time
("getTime()" indicates a different quantity now)
- Added pretty stars to background of all screens (this is accomplished
by basically keeping a single game world instance alive at all times &
recyling it between game runs, so let me know if you see any weird
inter-run issues...)
- Fixed a bug where pressing pause used a bomb as well