Fixed cluster logger issue reporting weird lag

• Added a feature to cluster logger. He now validates lag info. If replay time has travelled to the past, it is invalid. On instance restart, previous replay time is reset.
• repmgrd and automatic failover is not implemented, but I started to prepare fore it.
  • Added config file to add repmgrd automatic failover functionality to a postgres cluster with repmgrd.
  • Added a systemd unit file for repmgrd.