Limit the GET counts. Use service.
Limit the GET counts. Use service.

Now GET results for nb of returned channels and
nb of their values can be limited via HTTP req param.

Also, `service` is used to construct MQTT topic.

Signed-off-by: Drasko DRASKOVIC <83752d7d09cf86f69ee9aa9148577a17024773f3@gmail.com>

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