Change mapping variable labels

Change mapping variable label from 'Value column' to 'Observed value column' and change CT/scatterplot y/X axis labels to 'Observed Value' and 'Change from Baseline Value'

[mli1]

This is to align the labeling no matter what variable names the end users may have in the original listing. We go with the standard labeling across board

[xni7]

consolidate with #26