The configuration objects for specific notary implementations have been replaced
by a single untyped "extraConfig" Config object that is left to the notary service
itself to parse.
* Remove the raft bootstrapping command from node, we'll need a different
mechanism for that.
* Remove pre-generated identity config value.
* Split up obtainIdentity() in AbstractNode to make it easier to read.
* A temporary workaround for the bootstrapper tool to support BFT notaries.
* Update docs
* Add upgrade notes
* Fix rebase issue
* Add a config diff for the bft notary as well
