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 :)
* Update `github.com/ethereum/go-ethereum` package to 1.8.1 branch. Part of #638
* Fix code due to some signature changes. Part of #638
* use upstream for whisper backend
* Add patch to downgrade usage of Whisper v6 to v5 in some geth 1.8.1 vendor files. Part of #638
* Take into account the DNS rebinding protection introduced in 1.8.0 by adding exception for localhost. Part of #638
* Add patches required for cross-compiled builds starting with geth 1.8.0. Only applied during build. Part of #638
* Update expected JSON result in `TestRegressionGetTransactionReceipt()` and `TestCallRawResultGetTransactionReceipt()`. Part of #665
* Fix some failing e2e tests. Part of #638
* Address comments in PR #702. Part of #638
Andrea Maria Piana
Pedro Pombeiro
Adam Babik
Adrià Cidre