* Apply #pragma once in headers
* Adjust some thermistors formatting
* Misc cleanup and formatting

Implement AVR Platform

Includes:
  *firmware version / branch / date.
  *extruder count
  *board information (name, serial details, power supply type)
  *thermistors (names, min/max temperatures)
  *printer statistics (PRINTCOUNTER details)

Thanks to @thinkyhead for contributions.

Following up on #3231

to MELZI_MAKR3D.

Fix for #2288
As the normal MELZI also can have a 1284.

Hopefully this is helpful to organization and future expansion….

Hopefully this is helpful to organization and future expansion….

Hopefully this is helpful to organization and future expansion….