0.19.0

Changes:

• NetworkServer.EnqueueDataDownMACCommand has been refactored in order to
  support sending of mac-command blocks (guaranteed to be sent as a single
  frame). Acknowledgements on mac-commands sent throught the API will be
  sent to the NetworkController.HandleDataUpMACCommandRequest API method.
• NetworkController.HandleDataUpMACCommandRequest has been updated to handle
  blocks of mac-commands.
• NetworkController.HandleError method has been removed.

Note: In case you are using the gRPC API interface of LoRa Server,
this might be a breaking change because of the above changes to the APi methods.
For a code-example, please see the Network-controller
documentation.

Bugfixes:

• Updated vendored libraries to include MQTT reconnect issue
  (eclipse/paho.mqtt.golang#96).