* Add Metadata to messages, expose new messenger methods
This commits modifies deduplicator so that it takes a `StatusMessage`
instead of `WhisperMessage` and also returns a `Metadata` field which is
then passed back by the client when confirming messages, which fixes the
issue we had with not confirming pfs messages.
Currently PFS messages are decrypted and therefore modified before being
passed to the client. This make IDs computation difficult, as we pass
the whole object to the client and expect the object be passed back once
confirmed.
This changes the behavior allowing confirmation by ID, which is passed
to the client instead of the raw object.
This is a breaking change, but status-react is already forward
compatible.