Fix Craft Entity constructors and toStrings.

Also, standardise getHandle and clean up in general.
getHandle is now using the 'entity' member variable instead of
super.getHandle, as this reduces the number of chained calls needed.

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

@@ -11,9 +11,13 @@ public class CraftGiant extends CraftMonster implements Giant {
         super(server, entity);
     }
 
+    @Override
+    public EntityGiantZombie getHandle() {
+        return (EntityGiantZombie) entity;
+    }
+
     @Override
     public String toString() {
         return "CraftGiant";
     }
-
 }