Added getContents() to IInventory and implemented it.

Implemented Inventory and PlayerInventory and updated StorageMinecart and Slot.
Added getMaxStackSize to CraftItemStack.

src/main/java/org/bukkit/craftbukkit/CraftSlot.java

@@ -0,0 +1,25 @@
+package org.bukkit.craftbukkit;
+
+import org.bukkit.Inventory;
+import org.bukkit.ItemStack;
+import net.minecraft.server.Slot;
+
+public class CraftSlot implements org.bukkit.Slot {
+    private final Slot slot;
+
+    public CraftSlot(Slot slot) {
+        this.slot = slot;
+    }
+
+    public Inventory getInventory() {
+        return new CraftInventory( slot.b );
+    }
+
+    public int getIndex() {
+        return slot.a;
+    }
+
+    public ItemStack getItem() {
+        return new CraftItemStack( slot.c() );
+    }
+}