Update in-memory storage implementation to parse full address strings in
saveIdentity. Update usage of saveIdentity, passing in the full address string.
Reflect whether a saveIdentity operation reflects a replacement of an existing
key or not. The return value can be used by the caller to decide whether they
should clear sessions for the recipient.
Pass in a direction to isTrusted, based on constants defined by the storage
implementation. These values allow the trust store to determine whether a given
key is trusted, given the directional context.
