* WiFiClientSecure: add support for PSK (pre-shared key) ciphers

* add example for WiFiClientSecure PSK

* WiFiClientSecure: added README

* issue #2041

* handshake timeout

* seconds to milliseconds

If you develop on windows and need cr/lf files, see this:

    https://git-scm.com/book/en/v2/Customizing-Git-Git-Configuration#_formatting_and_whitespace

    Git can handle this by auto-converting CRLF line endings into LF
    when you add a file to the index, and vice versa when it checks out
    code onto your filesystem. You can turn on this functionality with
    the core.autocrlf setting. If you're on a Windows machine, set it
    to true - this converts LF endings into CRLF when you check out code:

    $ git config --global core.autocrlf true

* Added a lastError method to WiFiClientSecure so that a connection error from mbedTLS can be retrieved if connection fails (and then presented to a user).

* Changed to dos CRLF

* Made buffer size a const\nMore cleanup to match source

Update to make use of SSL a bit less confusing by ensuring errors are generated if the wrong method is called to retrieve the data stream. (#934)

* Fix possible infinite loop in the example

* Remove workaround of sockets always return -76 

Remove workaround of sockets always return -76 (because it's fixed on IDF now)
Remove delay during handshake (improving stability)

* Remove unusable mbedtls_net of context creation

* Fix bad destructor

* Compatibility with WiFiClient for HTTPClient

* Initial port from ESP8266

Changed SHA1 fingerprint by Root CA verification
Changed log system

* Remove deprecated function

* 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