Disaggregated primitive SDEs

[JPercival]

Needs additional information:

Measures can be defined to include SupplementalDataElements that me either Resources or primitive values. In some cases the primitive values should be aggregated (for example, the number of males across the entire population) for demographic purposes. In other cases we do not want to aggregate the values because they don't have any meaning when aggregated (for example, days since last appointment)