This worklog works as an umbrella to MySQL Group Replication
2nd milestone into 5.7. Children worklogs:
  WL#6826: GCS Replication: Interfaces for COMMIT Validation
  WL#6834: GCS Replication: Extract PKE for certification purposes
  WL#6839: GCS Replication: P_S table to show DBSM stats
  WL#6841: GCS Replication: P_S table to show GCS kernel stats
  WL#7206: GCS: Make the MTR rpl suite to work with GCS replication
  WL#7988: GCS: Pre-conditions verification
  WL#8250: GCS Replication: Transaction Applier Module [SERVER CHANGES]
  WL#8251: GCS Replication: Online distributed recovery [SERVER CHANGES]
  WL#8252: GCS Replication: Plugin [SERVER CHANGES]