[Bleeding] Add 1.7 setworldspawn and setidletimeout commands. Addresses BUKKIT-4932
Modify give command to support 1.7 features. Fixes BUKKIT-5286

Necessary additions include an interface to add internal value conversions
that are inappropriate for proper API design. This acts as a substitute
for properly formed, user-friendly commands in an effort to maintain
relatively vanilla behavior.
[Bleeding] Fix Achievement and Statistic API. Fixes BUKKIT-5305
[Bleeding] Add /achievement command. Addresses BUKKIT-4932
Add ServerListPingEvent player list API. Adds BUKKIT-5121, BUKKIT-2465
[Bleeding] Fix logic for calculating slot in Creative mode. Fixes BUKKIT-4715

Previously, hotbar slots for player inventory would return 9 - 18 while in
Creative mode, rather than 0 - 9. This commit fixes the logic used for
calculating the returned slot based on the raw slot.
Add methods to get and set knockback strength in Arrow. Adds BUKKIT-5103
Add setCritical and isCritical methods to Arrow.java. Adds BUKKIT-5113
[Bleeding] Add ProjectileSource interface. Addresses BUKKIT-1038, BUKKIT-1156
[Bleeding] Add setCharged and getCharged to WitherSkull. Adds BUKKIT-3060