This change will greatly simplify writing unit tests when a node is required but data persistence is irrelevant.
I also Introduced some refactoring and unit tests for `StatusNode`.
* Update project to use Whisper v6. Part of #638
* Revert "Add patch to downgrade usage of Whisper v6 to v5 in some geth 1.8.1 vendor files. Part of #665" - this reverts commit 6aefb4c8fd02dbcfffac6b69e8bb22b13ef86b6b.
* Enable light mode on Whisper v6 for non-mail servers. Part of #638
* Fix race condition in whisperv6/peer.go. Part of #665 (PR already accepted upstream for 1.8.2)
* Update bootnode addresses in staticnodes.json. Part of #638
* Add `shh.lightclient` flag and tests for bloom filter setting logic. Part of #638
* Move MakeTestNodeConfig to utils. Part of #638
* Reduce PoW in `whisper_jail_test.go` to fix flaky test. Part of #638
Adam Babik
Pedro Pombeiro