Add TwoColumnExpandingMapIterator
Add the ability to aggregate TabularResults
Allow multiple high dim results returned in 1 test
Support multi high dim vars in SingleOrMultConfig
Generalize TwoColumnsExpandingMapIterator

for when the context has only the concept path.
Remove redundant prop set
Make CompositeTabularResult support 1 result
Rename SingleOrMultiNumericVCC & change behavior

The change in behavior is that all the clinical data will always be
returned with a context (the values will be maps). In addition,
HighDimensionColumnConfigurator always includes the concept path in the
context in case multiConcepts is on. These two changes make the class
easier to use downstream by making the values that end up in BackingMap
more consistent in several cases.

However, the BoxPlot relying on having no context if there was only one
clinical variable, so it now has to switch between
ContextNumericVariableColumnConfigurator (the new name of the class) and
NumericColumnConfigurator.
Chg default missingValueAction to "Drop row"

This is what we want in large majority of cases.

Also probably fixes UAT-99, since the second column doesn't specify a
missingValueAction and the previous default was inappropriate.
Write extra PLOT_GROUP col in Line Graph
LineGraph Rscript has multiple plots for HDD data

The Rscript expects an extra column in the input data named PLOT_GROUP,
for which it will plot one LineGraph per unique value-group in that
column.