pretty-print command results

Most obvious change is for the command "Stats show", where the blob of stats data is now printed ina more readable fashion.
Also removed the print of 'send the command' line, and empty results are not printed at all

src/bin/bindctl/bindcmd.py

@@ -622,9 +622,11 @@ class BindCmdInterpreter(Cmd):
         if (len(cmd.params) != 0):
             cmd_params = json.dumps(cmd.params)
 
-        print("send the command to cmd-ctrld")        
         reply = self.send_POST(url, cmd.params)
         data = reply.read().decode()
-        print("received reply:", data)
+        # The reply is a string containing JSON data,
+        # parse it, then prettyprint
+        if data != "" and data != "{}":
+            print(json.dumps(json.loads(data), sort_keys=True, indent=4))