Offline Mode should fall back to soft RTC if fails to initialise config defined RTC

[tyeth]

If a user misconfigures an RTC in config, we could warn them in serial but continue with soft RTC rather than them come back to find no data on the SD card.

Maybe support lowercase like the component names too.

We could also detect the default time of new RTCs and warn the user to update the RTC for more accurate timestamp readings. The DS3231 appears to default to :1740604749 for the first reading in offline mode