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.
Spigot for 1.4.6. This commit has undergone basic testing and appears to now be safe for careful production usage. Please report any bugs to IRC as soon as you encounter them. Long live Spigot!
Update Maven Shade Plugin to version 2.0. Fixes BUKKIT-3213
Merge remote-tracking branch 'upstream/master'
Add BlockJukeBox for diff visibility
One record per JukeBox.
Allow fireworks to be created. Adds BUKKIT-3262