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

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

* Remove CI badges

Add Travis build badge

fixes: https://github.com/espressif/arduino-esp32/issues/145

fixes: https://github.com/espressif/arduino-esp32/issues/146

example:
```cpp
//done once on WiFi init
configTime(-7200, 3600, "pool.ntp.org");
//get local time
struct tm timeinfo;
if(!getLocalTime(&timeinfo)){
    Serial.println("Failed to obtain time");
    return;
}
//print time
Serial.println(&timeinfo);
//print time with different format
Serial.println(&timeinfo, "%A, %B %d %Y %H:%M:%S");
```
fixes: https://github.com/espressif/arduino-esp32/issues/29

fixes: https://github.com/espressif/arduino-esp32/issues/143

fixes: https://github.com/espressif/arduino-esp32/issues/144

* Add files via upload

enable pulseIn()

* Remove optimistic_yield