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.
Used to determine ACTUAL Living NPC's. Spigot mistakenly inversed the conditions for LivingEntity, and
used LivingEntity for Insentient Entities, and named the actual EntityLiving class EntityInsentient.
This should of all been inversed on the implementation side. To make matters worse, Spigot never
exposed the differentiator that there are entities with AI that are not sentient/alive such as
Armor stands and Players are the only things that do not implement the REAL EntityLiving class (named Insentient internally)
This interface lets you identify NPC entities capable of sentience, and able to move about and react to the world.
