New options for entity configurations.
SpawnCommand: A command to be run when the entity spawns.
BroadcastOnSpawn: What is to be broadcasted when the entity spawns. If not specified, nothing is broadcasted.
MaximumSpawnWave: The maximum wave the entity can spawn on.
Fixed issue where ZArena entities couldn't spawn in world guard regions with mob spawning disabled.
Fixed issue where yml files would, rarely, fail to load.
