Explicit temperature correction

[mdobres]

I have implemented the focuser on a Nano and it works well. (small form factor)
Needed to reassign temperatureSensorPin to A0 as Nano uses A4 & A5 for I2C used by display .
Note code also currently has:
temperatureSensorPin = 3; I think that should be A3 as Digital pin 3 already assigned.
Even with a 10K pot attached on a Nano the adjustable temperature range is too small. Would useful if there could be an explicit temperature offset factor.
Great project
TNX Max