[Grbl_Esp32 PR#565] Implemented first version of Pin class. DO NOT PULL!

!! DO NOT PULL !!

This is just a first version, as a WIP. What this is:

– An implementation of the Pin class, and everything needed to make that work.
– Mapping in the code to the Pin class.
– Made everything compile again.

What is missing and needs input from the team:

– PWM is now not implemented correctly / not at all. I currently just map them to native pins.
– Runtime configuration of Pins.
– Initialization does not work properly, because Pins are not runtime configured. This will probably crash the ESP the moment you attempt to run it, because of re-initializations.
– Some defines should disappear along with this. I made an ‘error-pin’ for this, but Assert functionality is currently incorrect. It will crash the ESP (which is good), but leaves the user in the dark…

Marked things with TODO FIXME as they needed more work.