[FEATURE] Load and Save the CMOS settings from disc

[RichardBrown384]

Is your feature request related to a problem? Please describe.
It would be very nice if the application could load/save the CMOS settings from disc.

Describe the solution you'd like

1. On application start the settings should be loaded
2. On application exit the settings should be saved.

Describe alternatives you've considered
None

Additional context
RISC OS 2 and 3 use the CMOS in slightly different ways and it would be nice to one CMOS file per OS version.
Possible ways to solve this would be to have

• a command line switch option
• use the CRC or hash of the OS ROM to determine which file to use

This is blocked by #7 and #8. The I2C and RTC should be tested before we save data passing through those systems to disc.