A1: add support for updated product variants, small fixes

This patch includes:
* generalize I2C slave access
* adapt CoinCraft Rig board selector to new design
* add support for single chip chains
* adapt verbosity levels
* check for chip clocks below 100MHz
Merge pull request #604 from zefir-k/A1.upstream.merge

A1: add support for updated product variants, small fixes