RPI*, BBW: need way to preserve private receiver data across SD card changes

[jbrzusto]

Unlike the BBBK, which has built-in flash RAM, the RPI* and BBW SGs have no persistent memory
off the SD card. So when a new (or reformatted) SD card is used, the SG loses:

• receiver crypto keys
• boot count
• deployment.txt
• any other config

One fix is to store such data with motus.org, and add a web interface capability to fetch from motus,
given motus login credentials.

[jbrzusto]

A major consequence of this issue is that data processing organized by bootnum will be scrambled.