BACKUP_SERVICE_ENDPOINT

[rsoika]

Introduce a new env param 'BACKUP_SERVICE_ENDPOINT' to indicate if a snapshot need to be backuped

See issue #170

In case this parm is set, the onSave method should create a separate event log entry used by the backupservice to backup a snapshot

    // 9. write event log entry...
    if (backupServiceEndpoint.isPresent() && !backupServiceEndpoint.get().isEmpty()) {
        if (debug) {
            logger.finest("......create event log entry " + EVENTLOG_TOPIC_ADD);
        }
        eventLogService.createEvent(EVENTLOG_TOPIC_ADD, snapshot.getUniqueID());
    }