v0.20.0: support Catena 4802; improve Si1133 driver
See release notes for details. Summary:
- Added support for the new MCCI Catena 4802 (4801 with better power management and temperature/humidity sensor on board)
- Updated the Si1133 driver to add 24-bit support for light measurement, and made more robust against sensor hangs
- Fix ADC operation when running at 2 MHz or 4 MHz clocks