Add Spawn Eggs for lacking existing mobs (Golems, Wither, & Ender Dragon)

Players used to be able to make spawn eggs for the mobs that lack them in older versions with NBT.

Instead of making us have to use commands or building shapes for the golems in Creative mode, give us the option to use spawn eggs for them.

For the specifically destructive mobs/bosses, put them in a Operator/Admin only creative tab that only shows up if you're an operator for ease of use.