Board from AI-Thinker

* Added boards constants for LED_BUILTIN and KEY_BUILTIN

Sources:
* esp320: http://wiki.sweetpeas.se/index.php?title=ESP320#Developing_using_the_Arduino_IDE
* esp32thing: https://cdn.sparkfun.com/assets/learn_tutorials/5/0/7/esp32-thing-schematic.pdf
* espea32: https://github.com/AprilBrother/ESPea32/blob/master/hardware/ESPea32-schematic.pdf
* hornbill32dev: https://github.com/ExploreEmbedded/Hornbill-ESP32-DEV/blob/master/Design%20Files/Schematic/Hornbill%20Devboard.pdf
* lolin32: values from existing header
* nano32: http://iot-bits.com/closer-look-esp32-nano32/
* node32s: https://github.com/lamloei/node32s-book/blob/master/ch01/node32s-schematic.pdf

* Replace BUILTIN_LED constant with #define

* Add build time partitions compilation

* Fix wrong definition of SS pin

* Add support for core debug level selection

* update idf libs

fixes: https://github.com/espressif/arduino-esp32/issues/76
fixes: https://github.com/espressif/arduino-esp32/issues/5
fixes: https://github.com/espressif/arduino-esp32/issues/91

* Add from original Arduino.h

* Add board "ESPea32"

* cleanup

* cleanup

* Change SS to 5