Changes

SPIGOT-1592: Implement ItemMeta for Spawn Eggs
The Minecraft implementation of spawn eggs is able to construct an
entity using all data that is present in the save format, however since
the Bukkit API has no such way to construct an entity unattached to a
world, and it appears creating such a way is a very challenging task,
the decision was instead made to add this API now that 1.11 has entities
which may not be represented by data values. In the future it may be
possible to implement a more expanded API cognate with this one.