This allows a websocket-in node to receive data, process it in a flow
and then send it back to the originating websocket client via a
websocket-out node.
Alternative implementation, closes#42
The username/password as not stored in the main flow file for security reasons;
they are stored in the adjacent credentials file. This does mean an extra step
to importing an MQTT node, as the user has to manually edit it to re-add username
and password if needed.
