Add `drone_uuid` to telegraf plugin

[giffels]

Currently, the telegraf the plugin sends only state changes of the drones to telegraf, however it does not include the drone_uuid, so that the information cannot be associated to a specific drone.

Feature request: Add drone_uuid to the record send to telegraf.

[giffels]

@rkleinem would like to work on this and submit a pull request.

[giffels]

@rkleinem: Should aim to include this in #315 ? Or do you think you need more time then ~1 week ? Please, take your time, if you need more. We can easily create another release later on.

[giffels]

Fixed by #318.