Thermocouple Daughterboard for Duet WiFi v1.1

This board is based on the MAX31855 chip so only Type K thermocouples are supported. The DuetWifi and DuetEthernet support up to two daughterboards, with a further two on a Duex2 or Duex5 expansion board, with 4 daughter boards a total of 8 thermocouples are supported. Thermocouple and PT100 daughterboards can be mixed and matched.