SERVER-14443 correct modeReplSet detection in ReplicationCoordinatorImpl::getReplicationMode()
SERVER-14443 implement canAcceptWritesForDatabase() and canServeReadsFor() in ReplicationCoordinatorImpl

also move replAllDead from master_slave to ReplicationCoordinator
SERVER=14443 implement isMasterForReportingPurposes() in ReplicationCoordintorImpl
SERVER=14443 implement buildsIndexes() in ReplicationCoordintorImpl