New User Extension and RTC Communication Fix

New/Added

A new user extension for a simple LoRa communication has been added. This can directly be used with an installed LoRa module on the H32, or it can be used as an example to roll your own user extensions (see directory Extensions).

Changed/Enhancements

Added an additional RTC alarm on startup for the edge case of the power dropping too much when turning on WiFi.
Added a check that restarts the ESP if RTC communication cannot be established. This takes care of (mostly theoretical) issues with the I2C communication protocol.
Changed return value of all methods of the Extension class to boolean, signalling success or failure.
Added methods api_call() and api_call_no_wifi() to the Extension class to allow independent sending of data.
Added method veto_backoff() to keep the backoff at the current value. This is needed to signal successful sending of data even if no WiFi connection has been established.

Fixed Bugs

Fixed two bugs in the PCF library, first, setting the month according to UNIX standard instead of the definition used by the PCF chip, second, setting the year according to UNIX standard instead of the definition used by the PCF chip. Now the RTC behaves correctly.
Ensure that the RTC is running correctly by setting the time before setting the alarm.