[Bleeding] Added DoubleChest wrapper so that DoubleChestInventory can return something other than null. Addresses BUKKIT-995

By: Celtic Minstrel <celtic.minstrel.ca@some.place>

paper-api/src/main/java/org/bukkit/block/DoubleChest.java

@@ -0,0 +1,47 @@
+package org.bukkit.block;
+
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.inventory.DoubleChestInventory;
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.InventoryHolder;
+
+public class DoubleChest implements InventoryHolder {
+    private DoubleChestInventory inventory;
+
+    public DoubleChest(DoubleChestInventory chest) {
+        inventory = chest;
+    }
+
+    public Inventory getInventory() {
+        return inventory;
+    }
+
+    public InventoryHolder getLeftSide() {
+        return inventory.getLeftSide().getHolder();
+    }
+
+    public InventoryHolder getRightSide() {
+        return inventory.getRightSide().getHolder();
+    }
+
+    public Location getLocation() {
+        return new Location(getWorld(), getX(), getY(), getZ());
+    }
+
+    public World getWorld() {
+        return ((Chest)getLeftSide()).getWorld();
+    }
+
+    public double getX() {
+        return 0.5 * (((Chest)getLeftSide()).getX() + ((Chest)getRightSide()).getX());
+    }
+
+    public double getY() {
+        return 0.5 * (((Chest)getLeftSide()).getY() + ((Chest)getRightSide()).getY());
+    }
+
+    public double getZ() {
+        return 0.5 * (((Chest)getLeftSide()).getZ() + ((Chest)getRightSide()).getZ());
+    }
+}

paper-api/src/main/java/org/bukkit/inventory/DoubleChestInventory.java

@@ -1,5 +1,7 @@
 package org.bukkit.inventory;
 
+import org.bukkit.block.DoubleChest;
+
 public interface DoubleChestInventory extends Inventory {
     /**
      * Get the left half of this double chest.
@@ -12,4 +14,6 @@ public interface DoubleChestInventory extends Inventory {
      * @return The right side inventory
      */
     Inventory getRightSide();
+
+    DoubleChest getHolder();
 }