Prince William and Kate Middleton have been left heartbroken after their dog Lupo died over the weekend.   The Duke and Duchess of Cambridge released a statement via their official Instagram account to mourn the dog.   Sharing a picture of their puppy, Kensington Palace wrote: “Very sadly last weekend our dear dog, Lupo, passed away. He has been at the heart of our family for the past nine years and we will miss him so much. – W & …