This commit does a few things:
1) Handle membership updates using protobuf and adds the relevant
endpoints.
2) Store in memory a map of chats + contacts for faster lookups, which
are then flushed to disk on each update
3) Validate incoming messages
Sorry for the large pr, but you know, v1 :)
* 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.
Pedro Pombeiro
Andrea Maria Piana