PNW Census: data model incorporating 903 data

[MichaelHanksSF]

Following #63 we need to create a single data model that incorporates data from both the 903 and census. The output will need to be defined with the client. In all likelihood, the PNW Census data will sit as an additional module of the 903 using the same child identifier keys and placement URN keys.

[MichaelHanksSF]

Unknown - need to pin down with client