Use transactions to skip mutex locks for reads and writes

* Added LEDC Fade exmaple

* Renamed LEDCFade example to LEDCSoftwareFade

Added valueMax parameter for ledcAnalogWrite

* Remove usage of LED_BUILTIN constant to solve CI errors

* Refactoring EPS32NVS library to Preferences library

* Renaming all set* functions to put
* Added functions for float, double and bool

* Small redesign of Preferences API

* added type to put* function names
* for (u)int64_t used functions name with *(U)Long64
* added functions for long and unsigned long (same like int a unsigned int)

fixes: https://github.com/espressif/arduino-esp32/issues/193

* Provide SSL/TLS functions to ESP32 with Arduino IDE

* Generate a new random number in case of reconnection

* Improved ESP32NVS default value support for read* functions

Fixed uninitialized NVS flash storage. Added example code.

* Add methods for String and remove unnecessary nvs_flash_init() in ESP32NVS class

+ other minor declaration fixes

* ESP32NVS function name renaming

* read* -> get*
* write* -> set*
* erase -> clear / remove

* Add new partition scheme

* Init NVS early, so it can be used without BT or WiFi

fixes: https://github.com/espressif/arduino-esp32/issues/191

Fixes: https://github.com/espressif/arduino-esp32/issues/173

Currently there is bug in WiFiUDP library when you want to use beginPacket(...) without listening on socket (without calling begin(...) first). You can't send any data because socket is not open and also tx_buffer is not allocated which cause crash while writing data to tx_buffer.

fixes: https://github.com/espressif/arduino-esp32/issues/51

Previous __FlashStringHelper implementation was defines as a char which brought problem in case the method with char* parameter used overloading with __FlashStringHelper* parameter (they was identical). Now __FlashStringHelper is defined as a class and all casts between char* and __FlashStringHelper* are made with reinterpret_cast sugar.

* Add Touchread example

* Rename libraries/ESP32/examples/Touch/TouchRead.ino to libraries/ESP32/examples/Touch/TouchRead/TouchRead.ino

* Update TouchRead.ino

* 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

* Add hint

* Update README.md

* Update README.md

* Update README.md

* Added a basic WiFi UDP client example: a sketch that sends random bytes over udp.

* Updated udp example and included Python and Ruby UDP servers.

* Initial version of build script for @PlatformIO; CI integration for Linux, macOS and Windows

* Remove CI badges

* Add @PlatformIO to Travis.CI