Release mega-20190817

Changes in mega-20190817 (since mega-20190813):

ESPEasy release bot (1):
      automatically updated release notes for mega-20190817

Gijs Noorlander (8):
      [LoRa/TTN] Document LoRaWAN/TTN controller
      [LoRa/TTN] Toggle visibility of OTAA/ABP parameters based on selection
      [LoRa/TTN] Reduce number of join requests
      [LoRa/TTN] Add Sample Set Initiator to mark samples of the same set
      [LoRa/TTN] Output packed raw format for uploading to TTN
      [LoRa/TTN] Add raw encoder/decoder for sysinfo plugin
      [LoRa/TTN] Add decoder for the packet header
      [LoRa/TTN] Correct decoder example in comments