[Web App]: Set up **optional** device registration in remote dashboard

[AJ-Koenig]

If users's don't want to self host their own MQTT server #115 then they'll need to use the shared, remote server. This requires device registration for the purposes of authentication and authorization.

In this feature we'll deliver a closed source web portal which users may access to register their device and then gain an access token which will be used on the remote MQTT server.