Make who can hear dragon death and wither spawn sounds configurable

Currently, whenever a dragon dies via damage or a wither completes it's spawning animation, a loud sound is sent to every player on the server. This PR allows server owners to set dragon death sounds as being sent to and only to players in that dragon's world, and the radius around which a wither's spawn sound will be heard. (A value of 0 or less (default -1) will revert to default behavior). Both settings' defaults emulate vanilla behavior.

These sounds usually freak players out when the occur for no reason and will allow server owners to remove these interruptions from players' server experience.

This PR works by modifying to whom a PacketPlayOutWorldEvent is sent, instead of being every player it is instead the players that should be hearing the sound. Again, not changing the settings will result in unmodified behavior.