Adds ${node} interpolation in topic option of configuration
Just like the clientid already works
Closes: #6431
feat(emqx_bridge_mqtt): bumped versions the right way
chore(appup): appups for mqtt bridge
feat(mqtt_bridge): test for bridge config
And also bumped one small version
chore(mqtt_bridge): updated CHANGES-4.3.md
fix(mqtt_bridge): conditional export
chore(mqtt_bridge): appup
And move emqx app back to root level
After realising the challenges of developing plugins in standalone
rebar projects. it is perhaps more smooth to keep using emqx as
a rebar dependency
JimMoen