Allows sharded search results to dedupe results by ID based on either the order of the shards in the shards param or by score. Allows the result returned to be deterministic. If by shards then shards that appear first in the shards param have a higher precedence than shards that appear later. If by score then higher scores beat out lower scores. This doesn't allow multiple duplicates because currently SOLR only permits a single result by ID to be returned.