Create native data model for dataset

[spikeheap]

The data received from LabKey is complete but structured in a difficult way to use within the UI. Specifically:

1. The metadata and data are separate, requiring a 2d lookup.
2. Date values are strings, and need coercing into Dates to be useful.

It makes sense to massage the server response into a custom object, maintaining as much information as possible whilst adding structure and making the model participant-centric to match our needs.