add SQL snippets to dump (meaningful parts of) the origin table

sql/origin-dump/.gitignore

+*.log

sql/origin-dump/origin-dump.sh

+#!/bin/bash
+psql -a service=swh-replica < origin-dump.sql > origin-dump.log

sql/origin-dump/origin-dump.sql

+\timing on
+\copy origin (type, url) to program 'pigz -c > origins.csv.gz' (format csv);