- rename to 'conservedSize' calculation for estimated conserved space
- add 'dupeUrls' to track duplicate URLs added on each crawl explicitly
- incrStat and type checking for stat types
- add removedCrawls and removedCrawlSize to track removed crawls
- clean up stats, add incrStat() to better keep track of stats in one place
add hash dupe when WARC record actually written
store savedSize as diff between original and revisit WARC records
indexer: compute savedSize by tracking subtracing revisit records to be added, if revisit added before original
- compute totalUrls, totalSize, uniqSize (uniqUrls = number of hashes) in per crawl key
- add stats on crawl commit, remove on crawl remove
- tests: update tests to check stats