Release mega-20190830

Changes in mega-20190830 (since mega-20190827):

Bartłomiej Zimoń (2):
      [DHT] start conversion improvements
      [DHT] fix timeout reading

ESPEasy release bot (1):
      automatically updated release notes for mega-20190830

Gijs Noorlander (9):
      [Settings Archive] Allow to download settings from some HTTP archive
      [Settings Archive] Documentation
      [Settings Archive] Only allow on core 2.5.0 and newer
      [Gratuitous ARP] Only send ARP packets when IF is up
      [PlatformIO] Changes for core 2.6.0 (Tasmota patched core)
      [Settings Archive] Allow to download settings from some HTTP archive
      [Settings Archive] Documentation
      [Settings Archive] Only allow on core 2.5.0 and newer
      Move dev build to core 2.6.0 (to make it fit)

stefan (7):
      Reduce bin size by excluding unneded parts
      Reduce bin size -- Typos.
      Reduce bin size -- changed macro definitions
      Reduce bin size -- add PubSubClient to #ifdef's
      Reduce bin size -- cast blynk code
      Reduce bin size -- enable all controller structs again
      Revert "Reduce bin size -- cast blynk code"