This is a substantial refactor of the consensus code and also introduces
a basic consensus simulation and testing framework. The new generic/templated
version is in src/ripple/consensus and documents the current type requirements.
The version adapted for the RCL is in src/ripple/app/consensus. The testing
framework is in src/test/csf.
Minor behavioral changes/fixes include:
* Adjust close time offset even when not validating.
* Remove spurious proposing_ = false call at end of handleLCL.
* Remove unused functionality provided by checkLastValidation.
* Separate open and converge time
* Don't send a bow out if we're not proposing
* Prevent consensus stopping if NetworkOPs switches to disconnect mode while
consensus accepts a ledger
* Prevent a corner case in which Consensus::gotTxSet or Consensus::peerProposal
has the potential to update internal state while an dispatched accept job is
running.
* Distinguish external and internal calls to startNewRound. Only external
calls can reset the proposing_ state of consensus
