Added burst-fire mode to projectile weapons
Made collision sounds not use entities
Base weapon now has effect entity

Now a weapon can more easily have screenshake and continuous sound.
Added sound util file
Removed unecessary minigun constructor field
Added support for projectile weapon shot sounds
Removed Doppler effect

It isn't really appropriate for this game.
Tweaked positional audio
qxMerge remote-tracking branch 'upstream/master'

Conflicts:
	entities/weapons/minigun.lua
Fixed shotgun