Move copy-index.sh to configuration repo

It will be used for several elasticsearch migrations, so it's not
specific to forums. Also it'll be updated to use logstash since
stream2es is unmaintained.

scripts/es/copy-index.sh

-#!/usr/bin/env bash
-
-#
-# Thin wrapper around stream2es.
-#
-# https://github.com/elasticsearch/stream2es
-# 
-# Copies an index from an elasticsearch source server to a target server. 
-# The target server can be the same as the source.
-#
-# Example:
-#
-# ./copy-index.sh http://localhost:9200 source_index http://localhost:9200 target_index
-#
-
-SOURCE_SERVER=$1
-SOURCE_INDEX=$2
-TARGET_SERVER=$3
-TARGET_INDEX=$4
-
-WORKERS="6"
-
-stream2es es -w ${WORKERS} --source "${SOURCE_SERVER}/${SOURCE_INDEX}" --target "${TARGET_SERVER}/${TARGET_INDEX}"