Entity package changes?

[bs2609]

1. These entity classes don't implement IMob, and aren't really hostile.
   Requesting a move from entity.monster to entity.passive for the following:

   • EntityGolem
   • EntityIronGolem
   • EntityPolarBear
   • EntitySnowman

2. These could do with a move from entity to entity.item:

   • EntityHanging
   • EntityLeashKnot

   Conversely, EntityXpOrb could do with moving from entity.item to entity.

3. The following could go in a new entity.npc package.

   • EntityVillager
   • IMerchant
   • INpc
   • NpcMerchant

4. Possibly having a entity.item.minecart sub-package for all the minecart classes ?

5. IProjectile seems to fit better in entity.projectile rather than just entity.

[liach]

Be careful that such package moves might hurt code compiles, for some of the package private methods may be broken in such renames.