Add logging

[jrleeman]

In an effort to diagnose the root cause of failures in flight due to electrical, mechanical, or environmental issues, we need to add logging every few seconds to a non-volatile on board memory.

• We'll use this FRAM chip
• Log these parameters: millisecond timestamp, instrument RPM, motor current, ambient temperature, which will be roughly 10 bytes for the full packet
• Log once every 10 seconds
• Keep a rolling log with a circular buffer
• Keep back a few bytes of storage for user parameter storage: cutoff enable, current limit, and a few reserved slots. Let's say the first 1k bytes are for this. That leaves us 255k bytes for logging, which should be around 70 hours.
• Dump command for dumping log to serial