Enchantment progress

-Add enchantability property for ToolLevels to make swords and tools able to be enchanted
-Proper handling of the enchantment window enchant slots
-Refactor some enchantment classes to API package
-Add EnchantmentRegistrar to API for plugins to register custom enchantments
-Rename "Enchantments" to "VanillaEnchantments" for all of Vanilla's enchantments
-Refactor Vanilla enchantments from material package to org.spout.vanilla.plugin.enchantment package

Right now, you should be able to place an item in the enchantment table and choose one of the three hard-coded enchant levels. This will "enchant" the item, although you cannot see it on the client.

Things needed to be done:
-The NBT data for enchantments is likely incorrect as there are client crashes when clicking items that have been enchanted. This issue is kind of a blocker for the rest of the code and I am not sure how to fix it, so it would be nice if someone could look through the Enchantment code and make sure all of the NBT data has been applied correctly.
-Once the above is complete, it will be easier to implement and test the actual enchantment-calculation code that will make Vanilla's enchantments ready for Beta.