Add public reference to kDatasetRawDataKey constant back in.
Add public reference to kDatasetRawDataKey constant back in.

cornelltech/AppCore,Sage-Bionetworks/AppCore,EricSiegNW/AppCore,ResearchKit/AppCore,jwarmkessel/AppCore,chb/AppCore,Sage-Bionetworks/AppCore,EricSiegNW/AppCore,andyvand/AppCore,Erin-Mounts/AppCore,Erin-Mounts/AppCore