MF-558 - Add MQTT subtopics documentation (#559)
MF-558 - Add MQTT subtopics documentation (#559)

* Added MQTT subtopic's doc section

Signed-off-by: nmarcetic <563861f1f7644bdda2dd6c3cebfddd9ab6b313f0@gmail.com>

* Resolving remarks

Signed-off-by: nmarcetic <563861f1f7644bdda2dd6c3cebfddd9ab6b313f0@gmail.com>

* Resolving remarks

Signed-off-by: nmarcetic <563861f1f7644bdda2dd6c3cebfddd9ab6b313f0@gmail.com>

* Resolved remarks

Signed-off-by: nmarcetic <563861f1f7644bdda2dd6c3cebfddd9ab6b313f0@gmail.com>

drasko/mainflux,drasko/mainflux,drasko/mainflux,Mainflux/mainflux-lite