Always connects with clean=true, even if there are subscriptions with qos > 0

[shaunco]

First off, awesome work!

It is fantastic that we can now set per-subscription qos values in the 0.4.0-beta1, however, MQTT Explorer always seems to connect with cleanSession=true, which resets any prior session for the client ID on the server and makes the qos=1 value act the same as qos=2.

Any chance you can expose a toggle that switches between cleanSession=true and cleanSession=false?

[shaunco]

Might be a dupe of #220