Reworked a lot of stuff to do with Smelting

src/main/java/com/gmail/nossr50/runnables/skills/FurnaceCleanupTask.java

@@ -0,0 +1,22 @@
+package com.gmail.nossr50.runnables.skills;
+
+import com.gmail.nossr50.mcMMO;
+import org.bukkit.block.Furnace;
+import org.bukkit.scheduler.BukkitRunnable;
+
+public class FurnaceCleanupTask extends BukkitRunnable {
+
+    private final Furnace furnace;
+
+    public FurnaceCleanupTask(Furnace furnace) {
+        this.furnace = furnace;
+    }
+
+    @Override
+    public void run() {
+        if(furnace != null && furnace.getInventory().getResult() == null) {
+            //Furnace is empty so stop tracking it
+            mcMMO.getSmeltingTracker().untrackFurnace(furnace);
+        }
+    }
+}