Adding Docker, some thoughts about MQTT handling

[dersimn]

Two points about the script itself:

• Default the mqttHost and mqttPort to the current browser location. This is very convenient if you set-up a web socket relay on ws://thisaddress/mqtt for e.g. with nginx. In this case the script will automatically connect to the broker right from the start.
• How about we implement an input line like your other scripts, where you put the whole URL (ws://user:pass@host:port/subpath) instead of specifying everything in an individual field? The paho web client [officially supports](paho web client) a whole URL as input, but in my experience it doesn't work yet. Until then we could use an regex workaround to extract the data.
• Is it really necessary to subscribe the $SYS/# things? Do we gain any information from that? It kinda looks weird in the status tab, t.b.h.