This fixes a CRITICAL missing part of the Bukkit API due to mistakes on upstream
refusing to implement the Sentient NPC baseclass of all NPC's.
Until now, the Bukkit API has not provided a way for accessing and setting
a non creature entities target.
Although Flying, Slime, Ambient, and Water mobs all supported targets internally,
you were unable to get/set it.
Now with the SentientNPC API and these API's moved down, every sentient NPC has
access to target data.
