[WIP] Add bare bone implementations for some Entities

So, I started out to implement all known Entity interfaces from Bukkit API (and some from Minecraft), but as of late, I do not have the time to produce said implementations with all the proper storages, hooks and missing APIs.

I'm opening this PR in hopes that someone may pick up where I left off. This PR is dependent on https://github.com/gabizou/Bukkit/tree/glowstone-entity-1.8-update for some of the 1.8 entities (Guardian, Rabbit, and Endermite). 
That is useless if you don't `return entity`.