Update in-memory storage implementation to parse full address strings in
saveIdentity. Update usage of saveIdentity, passing in the full address string.
This was mostly used internally by SessionRecord to flag the lack of an
open session, but that can be replaced with an actual check for an open
session.
This is redundant to the identity key store, and only used to check
internal consistency between sessions and the 'current' remote identity,
though there's no particular reason we can't keep sessions from previous
identity keys.
