The signature of the `Raw` methods has been changed so that they return
the application messageID.
Clients will keep track of this ID and receive a notification through
the envelopesMonitor of the state of the envelopes (sent/expired).
Envelopes monitor is passed this ID as well.
We use an array of IDs as datasync messages might be batched.
status-go requires some special methods to be exposed in order to support the current integration.
Introduced families of methods marked as `DEPRECATED`:
* `SendRaw` to send transit-encoded messages, both public and private. It supports only private PFS-enabled messages. To send private non-PFS messages, we can add this functionality or it needs to happen through `shh_post` directly from status-react.
* `RetrieveRawAll` and `RetrieveRawWithFilter` to get retrieve decrypted but transit-encoded messages.
* `LoadFilters` and `RemoveFilters` to manage Whisper filters directly.
* By default, persistence of messages is disabled. It can be enabled with an option passed to `Messenger`.
* File paths to the databases are configurable in `Messenger`.
Andrea Maria Piana
Adam Babik
Pedro Pombeiro
Adam Babik