Replace all fastDigitalRead/Write() with READ/WRITE()
Define SCK_PIN, MISO_PIN, MOSI_PIN in pins.h if not already defined in the pins_*.h files.
Remove these conditional pin definitions from the pin-files. They are now always defined.
Define separate sets of SPI-pins for AT90USB with and without Teensy support in fastio.h.
Likely this was the main reason for all that confusion about the AT90USB-SPI pins.
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.
The PrintrBoard Rev F utilizes a mcp4728 DAC to set motor current. Printrbot's implementation utilizes 2 new M-codes to set and write the DAC settings to the DAC EEPROM: `M909` (Read DAC) and `M910` (Write DAC). `M907` is re-used to set value, `M908` for direct control.
The Pins file for the RevF board is included.
