GA Release v1.4.475

node health:

- db: PK is on (hostname, token)
- aggressively written to, every 10 seconds
- aggressively purged (expire = insert interval * 2)
- written to also by CLI instances

recovery:
- added AcknowledgeCrashedRecoveries(): auto-acknowledge (mark as
failed) recoveries owned by a now-dead process. This is detected using
the above node health changes.