add DupDetector::GetUniquePosList() to get the unique docid positions in original list.
add DupDetector::GetUniquePosList() to get the unique docid positions in original list.

izenecloud/idmlib,izenecloud/idmlib,izenecloud/idmlib,pombredanne/idmlib,pombredanne/idmlib,izenecloud/idmlib,izenecloud/idmlib,pombredanne/idmlib,pombredanne/idmlib