This commit pegs the clock value to maximum + 120 seconds from the whisper
timestamp.
In this way the we avoid the scenario where a client makes the timestamp
increase arbitrarely.
* Use a single Message type `v1/message.go` and `message.go` are the same now, and they embed `protobuf.ChatMessage`
* Use `SendChatMessage` for sending chat messages, this is basically the old `Send` but a bit more flexible so we can send different message types (stickers,commands), and not just text.
* Remove dedup from services/shhext. Because now we process in status-protocol, dedup makes less sense, as those messages are going to be processed anyway, so removing for now, we can re-evaluate if bringing it to status-go or not.
* Change the various retrieveX method to a single one:
`RetrieveAll` will be processing those messages that it can process (Currently only `Message`), and return the rest in `RawMessages` (still transit). The format for the response is:
`Chats`: -> The chats updated by receiving the message
`Messages`: -> The messages retrieved (already matched to a chat)
`Contacts`: -> The contacts updated by the messages
`RawMessages` -> Anything else that can't be parsed, eventually as we move everything to status-protocol-go this will go away.
Andrea Maria Piana
Pedro Pombeiro
Adam Babik