Upgrade to ESP-IDF 4.0

[renzenicolai]

ESP-IDF v4.0 has been released, we should start upgrading our codebase to use this new version of the SDK.

https://github.com/espressif/esp-idf/releases/tag/v4.0

One possible solution would be to start with an empty hello world project based on the new SDK and move over all our functionality one driver at a time.

The Python interpreter should be upgraded too as the upstream micropython project now has support for IDF v4.0 too: https://github.com/micropython/micropython/tree/master/ports/esp32

[renzenicolai]

Thanks to @jorisplusplus this planned upgrade will finally be a reality. He put a proof of concept for us to start working with here: https://github.com/jorisplusplus/new-ESP32-platform-firmware/