HBASE-11025 Infrastructure for pluggable consensus service (Mikhail Antonov)

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1589537 13f79535-47bb-0310-9956-ffa450edef68
HBASE-11025 Infrastructure for pluggable consensus service (Mikhail Antonov)

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1589538 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch 'ASF_HBase_remote/trunk' into trunk
Merge remote-tracking branch 'origin/trunk' into wandisco_integ