Trade Registration Fix

Delays initialization of registered trades (hookshot upgrade list) until server start.
This fixes my problems with the Hookshot upgrades, and doesn't appear to cause any problems.
Fixes #18.
/**
	 * Call during FMLPreInitializationEvent to initialize and register all items.
	 */
	public static void init() {
		ZSSItems.initItems();
		ZSSItems.registerItems();
		ItemChuJelly.initializeJellies();
		ItemHeroBow.initializeArrows();
		ItemSlingshot.initializeSeeds();
		ZSSItems.addDispenserBehaviors();
	}