Added checks to weapon effect functions

Just so they don't throw an error if you try to use them while not
firing.
Fixed some sounds not being affected by game speed
Tweaked death explosion radius
Tweaked default shotgun spread
Tweaked death explosion damage
Tweaked the shotgun's firing pattern
Tweaked shotgun
Made test bots all different colors

Also added a color util file with a HSV-to-RGB function.
Made all sounds use sound source entities

This is so they can all be adjusted for game speed in real time.
Cleaned up references to util.sound
Made the game basically pause when game speed == 0
Merge branch 'master' of https://github.com/legospacy/rainbow-arena
Put rotation line drawing in CircleColor
Moved world init logic to new file

I need to overhaul the world logic, and this is the first step. More
changes to come.

I also made the timer per-world instead of using a global one.
Made timer update stop when speed == 0

Also added TODO about overhauling screenshake.
Overhauled world util
Replaced lots of camelCase with underscores

...to make it consistent.
WIP: Got game to not crash after overhaul
Fixed physics collision sound
Added TODO about burst fire projectile weapons