Implement 1.4.6 ItemMeta. Adds BUKKIT-3236, BUKKIT-3237

Some meta functionality is refactored into common methods.

CraftItemStack uses the ItemMetaKey identifiers for enchantments.

Refactored unit test to include extra functionality; initially only
checking the presence of the DelegateDeserialization annotation.
Use max inventory size for new stack. Fixes BUKKIT-3240
Add a null check for Item Entities. Fixes BUKKIT-3249
Fix command line arguments being ignored. Fixes BUKKIT-3247
Don't save server properties when it's read only. Fixes BUKKIT-3250
Fix loading Items entities with an invalid item. Addresses BUKKIT-3249
Update enchantment handling to 1.4.6. Fixes BUKKIT-3256
Check file existence before determining readOnly. Fixes BUKKIT-3255
Zero is not less than zero. Fixes BUKKIT-3259
Added TileEntitySkull for diff visibility
Implement Skull BlockState. Adds BUKKIT-3259
Implement API to get and set FireworkMeta on Firework entities
Updated version to 1.4.6-R0.1 in pom.xml for Beta.
Updated version to 1.4.6-R0.2-SNAPSHOT for development towards next release.
Add BlockJukeBox for diff visibility
One record per JukeBox.
Allow fireworks to be created. Adds BUKKIT-3262
Add DispenseBehaviorFireworks and EntityFireworks for diff visibility
Fire BlockDispenseEvent for fireworks. Adds BUKKIT-3246
Update firework power when modifying meta. Fixes BUKKIT-3272