* Add CA certificate in example

SHA1 fingerprint is broken now: more info: https://shattered.io

* Best error handling

When occur an error in WiFiClientSecure library just return the error message
and clean the context avoiding crash - fix for https://github.com/espressif/arduino-esp32/issues/211

Translate MbedTLS error codes in messages for best understanding

* Declarate certificates as const

mbedtls_pk_parse_key needs a const unsigned char * certificate. In old implementation the certificate was declarated as char * so first it converts to unsigned and after to const.

When we convert signed to unsigned it may result in a +1 larger output.

Fix issue https://github.com/espressif/arduino-esp32/issues/223

* Provide SSL/TLS functions to ESP32 with Arduino IDE

* Generate a new random number in case of reconnection