RTC rework
Pre-release
Pre-release
Rework RTC calendar to use a elapsed seconds offset (BKPx); this way RTC once started does not have to be modified
Use a S11 value for subsecond correction throu PPS (BKPx)
Use RTC for millis() over Systick
Add LSE calibration via TCXO for CMWX1ZZABZ (via DIO1)
Add PPS tracking for GNSS to facility RTC phase correction