Changes

Summary

1. Add API to manipulate boss bar of entities and those created by commands (details)

Commit dfbb9a1c9e32240fc52c0c10d69070ccf1551840 by md_5 (md_5) Add API to manipulate boss bar of entities and those created by commands
	src/main/java/org/bukkit/Server.java
	src/main/java/org/bukkit/entity/EnderDragon.java
	src/main/java/org/bukkit/Bukkit.java
	src/main/java/org/bukkit/boss/KeyedBossBar.java
	src/main/java/org/bukkit/entity/Boss.java
	src/main/java/org/bukkit/entity/Wither.java