MODE-1876 Removed expensive ops to allow reindexing large repositories 

Recently the reindexing operations were changed so that upon "IF_MISSING" any already-indexed node would be skipped. However, this was not really the intention of the "IF_MISSING" option, and the logic to determine which nodes were already indexed was quite expensive. Therefore, the logic was changed to reindex the entire repository's content whenever the indexes were missing (e.g., either empty or not yet created).