Expander cannot be flashed

[falkoschindler]

Currently there is an issue flashing the expander, causing it to crash with a backtrace. We assume the problem is due to a different partition table in version 0.1.12. So when updating an expander from some version like 0.1.5 to 0.1.11, it works well. But upgrading to 0.1.12 fails.

Maybe we can make CONFIG_PARTITION_TABLE_OFFSET an optional parameter for core.flash() to work around these edge cases. Or we describe how to OTA-update the expander in the readme. As long as we don't change the partition table in the near future, a temporary fix might be good enough.

[falkoschindler]

Or we describe how to OTA-update the expander in the readme.

We noticed that this is not an option, because the firmware on the expander doesn't know the ota() command. So we need to fix the flash() command to work with arbitrary partition tables on the target ESP.

[JensOgorek]

Fixed with PR: #56