support JSON subtopics in hyperdash

[kollokollo]

Currently this is not yet working but I am working on this. Read more about this in the MQTT Topic Payload Convention

[kollokollo]

So currently the JSON-Subtopics can now be displayed. However, publishing to them is not yet possible. Also I have not implemented them into the rule engine framework. However MQTT-Hyperdash is much more flexible now and accepts values from commercial devices which in most cases produce JSON output.

[kollokollo]

What is still missing is the subtopics support for the rule engine framework.