* 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
Currently it is quite easy to introduce concurrency issues while working
with transaction object. For example, race issue will exist every time
while transaction is processed in a separate goroutine and caller will
try to check for an error before event to Done channel is sent.
This change removes all the data that is updated on transaction and leaves
it with ID, Args and Context (which is not used at the moment).
Signed-off-by: Dmitry Shulyak <yashulyak@gmail.com>