Make SPI pins configurable

[ottonemo]

I wanted to be able to choose which pins the SPI uses for communication but this was not yet possible.
The default values for the pin assignment are still < 0 so the default values should apply and the change
should be backward compatible.

I also noted that there is a hard coded analogue read on pin 0 to get a random seed.
The ESP32-S2 for example has no ADC on pin 0 which will make it fail.
Is this already on the roadmap?

[sabas1080]

@ottonemo Thanks for your contribution but it seems that pullrequest has not passed the unit tests, please review

[sabas1080]

the best way to do this would be to create instances so that the defined ports can function.