Merge pull request #89 from atlasapi/image-persistence-order

Don't use HashSet when deserializing images from mongo
Check children of equivalent containers for available locations

When resolving identifiers of available children of a container check
the children of the container's equivalents. Available children of the
equivalents are transformed back to the children of the primary
container via resolution of their lookup entries.
Merge branch 'mbst-6296-available-locations' into stage

* mbst-6296-available-locations:
  Check children of equivalent containers for available locations