This previously happened in the extension SQL code, which could
potentially cause replay problems if installing on a BDR cluster.
As this table is only required for streaming replication failover,
move the initialisation to "repmgr primary register".
Addresses GitHub #344 .
There are now too many options to sensibly fit into general --help
output; we'll add separate output for each repmgr command, e.g.
"repmgr node --help".
For logging an event to the event table without generating an external
event notification.
Rename existing create_event_record*() functions to create_event_notification*()
as this describes their function better.
This is only relevant when cloning a standby and the node's upstream
can change after failover/switchover etc., so no point keeping the
original value around in the configuration file.
