Merge pull request #438 from atlasapi/content-msg-id

EquivalenceUpdatingWorker handles msgs with content id not URI
Merge pull request #439 from atlasapi/stream-equiv-consumers

Add env properties to control equiv update stream consumer count
Only update equivalence from stream for content without prev result
Merge branch 'new-only-equiv-update' into stage

* new-only-equiv-update:
  Only update equivalence from stream for content without prev result