Subset patrolling support

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Apparently not everyone knows what meta-data stripping is, so some people end up with thumbnails embedded in JPEGs messing up binary dedupe.

Some of these problems were found in considerably large collections so batch fixing might be a problem for the inevitable patrolling read that needs to come afterwards. So, we need to support the curator patrolling a subset of files, perhaps even being the orchestrator of these batch commands so it can safely & automatically do the necessary index updates afterwards.