Fix findTarget() in PigZombiePet
Do proper damageEntity if owner is null too
Add Enderman Pet
Only issue I can note on this right now is that Enderman aggro when looked at, not really sure what to do to prevent it.

They still pickup blocks and dislike the water. Though those are how Enderman behave so I don't really think a pet version should be much different.
Signed-off-by: Steven Downer <grinch@outlook.com>