Add method to get the source of a TNTPrimed. Adds BUKKIT-3815

src/main/java/org/bukkit/craftbukkit/entity/CraftTNTPrimed.java

@@ -1,8 +1,10 @@
 package org.bukkit.craftbukkit.entity;
 
+import net.minecraft.server.EntityLiving;
 import net.minecraft.server.EntityTNTPrimed;
 
 import org.bukkit.craftbukkit.CraftServer;
+import org.bukkit.entity.Entity;
 import org.bukkit.entity.EntityType;
 import org.bukkit.entity.TNTPrimed;
 
@@ -50,4 +52,17 @@ public class CraftTNTPrimed extends CraftEntity implements TNTPrimed {
         return EntityType.PRIMED_TNT;
     }
 
+    public Entity getSource() {
+        EntityLiving source = getHandle().getSource();
+
+        if (source != null) {
+            Entity bukkitEntity = source.getBukkitEntity();
+
+            if (bukkitEntity.isValid()) {
+                return bukkitEntity;
+            }
+        }
+
+        return null;
+    }
 }