Updated inventories to a has-a relationship.

Added PlayerInventory interface with playeronly methods.
Add equals to ItemStack.

src/main/java/org/bukkit/Slot.java

@@ -3,39 +3,25 @@ package org.bukkit;
 /**
  * Represents a slot in an inventory
  */
-public class Slot {
-    private Inventory inventory;
-    private int index;
-
-    public Slot(Inventory inventory, int index) {
-        this.inventory = inventory;
-        this.index = index;
-    }
-
+public interface Slot {
     /**
      * Gets the inventory this slot belongs to
      * 
      * @return The inventory
      */
-    public Inventory getInventory() {
-        return inventory;
-    }
+    public Inventory getInventory();
 
     /**
      * Get the index this slot belongs to
      * 
      * @return Index of the slot
      */
-    public int getIndex() {
-        return index;
-    }
+    public int getIndex();
 
     /**
      * Get the item from the slot.
      * 
      * @return ItemStack in the slot.
      */
-    public ItemStack getItem() {
-        return inventory.getItem(index);
-    }
+    public ItemStack getItem();
 }