AxxSolder v3.2.2

Stable release of AxxSolder v3.2.2

Changes from previous release (AxxSolder v3.2.1):

• Implement temp calibration as 6-point calibration with linear fitting
  The user can now calibrate the temperature at 6 temperature points: 100 - 200 - 300 - 350 - 400 - 450 deg C. The temperature is then scaled linearly between these calibrated points.
• Implement separate I gain multiplier for negative error and adjust PID values
  The PID controller is improved by updating the conditional integration handler and implementing un-symmetric I gain.
• Make Serial DEBUG print an user option
  The UART debug output can be turned ON/OFF from the SETTINGS menu.

Outputting the DEBUG data allows to plot temperatures, power, setpoint, P, I and D parts of the PID and measured current.
This is very useful when tuning the PID and this is an example: (C210-008 tip on 24 VDC)

This is plotted with the software "SerialPlot".
The SerialPlot config is availible here:
https://github.com/AxxAxx/AxxSolder/blob/main/Other/SerialPlot_settings.ini