Automatically calculate and save calibration information when the minima is started for the first time

[sarfata]

Ideally, the minima software should ask me to choose which si570 I have in a list when I start it for the first time. It would then do the math and save that in the eeprom.

How it works:

• Show a list of different minima reference number and we know the associated startup frequency.
• Get the si570 registers at startup (they have been calibrated at the factory for this frequency)
• Calculate the actual crystal frequency and save it in eeprom
• Reload it automatically on next startups