Usable for library developers who write code not dependent on Arduino.
Adding 3 lines to the includes will permit their debug messages to be
visible in Arduino IDE or when enabled under IDF

* Update IDF to de750e9

* Add BLE Library submodule

Added argument to HardwareSerial.begin to specify whether the logic levels of the UART rx and tx lines should be inverted (#719)

* ESP32 default port in comment

* ESP32 default hostname.

Fixes: https://github.com/espressif/arduino-esp32/issues/710

* Create ledcWrite_demo_ESP32_RGB.ino

adding the public domain example ledcWrite_demo_ESP32.ino to this repo.  Added RGB to the name for people searching, added some comments, and renames things to make a bit more sense.

* Update ledcWrite_demo_ESP32_RGB.ino

renamed to ledcWrite_RGB.ino and added a couple more comments based on https://github.com/espressif/arduino-esp32/issues/689

* Rename libraries/ESP32/examples/AnalogOut/ledcWrite_demo_ESP32_RGB/ledcWrite_demo_ESP32_RGB.ino to libraries/ESP32/examples/AnalogOut/ledcWrite_RGB/ledcWrite_RGB.ino

Renamed.

Fixes: https://github.com/espressif/arduino-esp32/issues/708

Fix redefines of strXXX, original was using strnXXX with length set to 0x7fffffff.  This caused problems with strcpy and strcat. The destination buffer was NULL'd to 0x7fffffff which killed the app.

* Chip revision fix

https://www.esp32.com/viewtopic.php?f=2&t=1358&sid=f77cd62ec254317f3bbb30d8ab75ca2a&start=10

* using of esp_chip_info instead of register reading

Fixes #694

* Print error when serial number is invalid

* Move to the first check, change end by return

Use UTC instead of CDT for consistency

This reverts commit c2406749.

* Addition of a i2cReset method and timeout handling for the case where the i2c hardware FSM (state machine) gets stuck in a busy state.

* Use newly added i2cReset function within the wire library.

* Add example to update ESP32 via SD card

* Delete update.bin from sd upon finishing update

* remove precompiled binary from example

* Check whether update.bin is a file

to be same as SPIFFS

* Added ESPNow basic example

* fixed meta doc for slave

* refactored folder structure

* bug fixes

* Added Single Master Multi-Slave

* updated meta docs

* Update README.md

* Create opensuse.md

* Added ESPNow basic example

* fixed meta doc for slave

* refactored folder structure