Add cluster cmdline parameter for indexer

Indexer now accepts cluster address instead of projector address
as discovery endpoint for kv addresses.

Change-Id: Ief9071f831ad3b5f59ec3fe2aabd9c7b5420796a
Reviewed-on: http://review.couchbase.org/43680
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>