Add a camel entity

[codetaylor]

Adds a camel entity with the following features:

• Camel entity spits at player / hostile mobs if attacked
• Camel entity wander when untamed
• Camel entity will seek out and occasionally eat grass / drink water
• Camel entity will occasionally turn head slightly
• Camel entity walking animation
• Camel entity eating / drinking animation
• Camel entity spawn egg
• Camel entity follows the player when tamed
• Camel entity sits and stays put when right-clicked
• Camel entity is tameable with 4 wheat
• Camel entity is breedable with 1 wheat
• Camel entity sitting / standing animation