#1 DS18B20: sometimes sensor readings are wrong for 1 sample

When this happens the DallasTemperature lib returns a temperature reading of exactly 85 °C which seems to be some error code.

As DS18B20 sensors are used to monitor heating feed/return 85°C is a plausible value, so this needs at least some smart filtering.

Also DallasTemperature does not seem to do a CRC check. Maybe better switch to OneWireOG lib instead.

fixed with d5d331e05b -> filter 85° readings if last reading was <80 or >90 -> increase precision of OneWire sensors to 12 bit