Make item stack accessible in item query.

src/main/java/li/cil/oc2/api/bus/device/provider/ItemDeviceQuery.java

@@ -1,4 +1,7 @@
 package li.cil.oc2.api.bus.device.provider;
 
+import net.minecraft.item.ItemStack;
+
 public interface ItemDeviceQuery extends DeviceQuery {
+    ItemStack getItemStack();
 }

src/main/java/li/cil/oc2/common/bus/device/provider/Providers.java

@@ -29,6 +29,7 @@ public final class Providers {
         addProvider(new ItemHandlerDeviceProvider());
         addProvider(new TileEntityDeviceProvider());
         addProvider(new BlockDeviceProvider());
+        addProvider(new MemoryItemDeviceProvider());
     }
 
     public static void addProvider(final DeviceProvider provider) {
@@ -101,5 +102,10 @@ public final class Providers {
         public ItemQuery(final ItemStack stack) {
             this.stack = stack;
         }
+
+        @Override
+        public ItemStack getItemStack() {
+            return stack;
+        }
     }
 }