Optionalize units argument.

[samussiah]

Measure dropdown options should include units.

[jwildfire]

Can you provide a bit more detail in the description? What happens in 2.0.0 if units aren't provided?

[samussiah]

The issue here is ADaM data where units are not necessarily standardized and measures may have more than one associated unit. In ADaM the units are concatenated to the measure in a single variable named PARAM.

In order to distinguish records within a measure with differing units MEASURE_COL needs to include units. ADaM already does this. We could take the renderer two directions:

1. Make UNITS_COL optional and assume values of MEASURE_COL are unique for each unit, as is currently implemented in safety-histogram.
2. Concatenate MEASURE_COL and UNITS_COL within the renderer.