* Persistent sessions can survive node/connection process down
* Internal SessionID is generated, external ClientID is as before
* Sessions are persisted to mnesia
* A session router is added in parallel to the ordinary router
* Messages that are subscribed to by a persistent session are
persisted by publisher
* Information about persisted and delivered messages are stored in
mnesia per session.
* A resume protocol similar to takeover is implemented for resuming
from mnesia
* Can be configured (and enabled) by the top lever config
"persistent_session_store"