Bring protocols into line with spec
- BQP should ignore records with unknown versions/record types
- BSP should ignore records with unknown versions/record types
- BSP should use "record" rather than "packet"
- Max message body length should be 2^15 bytes (32 KiB)
- Max group descriptor length should be 2^15 bytes (32 KiB)
- Message ID should hash group ID, timestamp, body as separate arguments