as proposed by https://github.com/esp8266/Arduino/pull/6972#issue-358508056.
@ttytyper 's changes have been incorporate into this PR
The build flag ARDUINO_SONOFF_... should now appear as ARDUINO_ESP8266_SONOFF_...
@ttytyper, @mcspr, and @d-a-v thanks!
* Add boards filter support - allows for the creation of an abridged boards.txt.
Add some of the ITEAD Sonoff boards to boards.txt.py.
Minor reorder of presentation of board menu items, mainly grouped
board Model and module selection to the top.
* Corrected, I think, LED_BUILTIN vs BUILTIN_LED??
* Updated boards.txt
* Added support for DOIT ESP-Mx DevKit (ESP8285) board.
Adjusted wording and fixed side bar formating issue on the
Sonoff description. Also, removed resetmethod menu
and assigned resetmethod of none.
