Add support for deleting a conversation

Note that the conversation record is not actually destroyed,
merely marked inactive, preserving the contact name, photo,
etc...

index.html

@@ -50,6 +50,7 @@
                         <li>by <a href="http://whispersystems.org">Open Whisper Systems</a></li>
                         <li><a href="http://support.whispersystems.org/">Need Help?</a></li>
                     </ul>
+                    <button class='destroy'>Delete this conversation</button>
                 </div>
             </div>
         </script>