[Bleeding] Implementation of inventory framework. Addresses BUKKIT-856

See the corresponding Bukkit commit for details.

Implementation details:
- Any packets that include an itemstack will send air stacks as null; maybe this will even eliminate the client crash that occurs if the client receives an air stack
- Better handling of null itemstacks in general (ie less converting them to air stacks)
- Inventory.setContents() can now take an array smaller than the inventory without error
- Player.updateInventory() should now correctly update the result slot in a crafting inventory

Some small credit goes to Afforess (initial implementation of openInventory() methods) and Drakia (initial implementation of InventoryOpenEvent and InventoryCloseEvent).

src/main/java/net/minecraft/server/InventoryLargeChest.java

@@ -1,12 +1,23 @@
 package net.minecraft.server;
 
+// CraftBukkit start
+import java.util.ArrayList;
+import java.util.List;
+
+import org.bukkit.craftbukkit.entity.CraftHumanEntity;
+import org.bukkit.entity.HumanEntity;
+import org.bukkit.inventory.InventoryHolder;
+// CraftBukkit end
+
 public class InventoryLargeChest implements IInventory {
 
     private String a;
-    private IInventory b;
-    private IInventory c;
+    public IInventory b; // CraftBukkit - private -> public
+    public IInventory c; // CraftBukkit - private -> public
 
     // CraftBukkit start
+    public List<HumanEntity> transaction = new ArrayList<HumanEntity>();
+    
     public ItemStack[] getContents() {
         ItemStack[] result = new ItemStack[this.getSize()];
         for (int i = 0; i < result.length; i++) {
@@ -14,6 +25,26 @@ public class InventoryLargeChest implements IInventory {
         }
         return result;
     }
+
+    public void onOpen(CraftHumanEntity who) {
+        b.onOpen(who);
+        c.onOpen(who);
+        transaction.add(who);
+    }
+
+    public void onClose(CraftHumanEntity who) {
+        b.onClose(who);
+        c.onClose(who);
+        transaction.remove(who);
+    }
+    
+    public List<HumanEntity> getViewers() {
+        return transaction;
+    }
+    
+    public InventoryHolder getOwner() {
+        return null; // Double chests technically have multiple owners, so there's no sensible way to pick one
+    }
     // CraftBukkit end
 
     public InventoryLargeChest(String s, IInventory iinventory, IInventory iinventory1) {