Populating json colorbar file with environmental variables

[jwarner8]

Currently, json entries are fixed for specific variables (where cmap is defined, along with min/max value for colorbar). Some diagnostics much need adaptive colorbar ranges, such as the age of air diagnostic. This colorbar will extend from 0 to the length of the forecast, defined as $CSET_ANALYSIS_PERIOD. Is there a way we can use $CSET_ANALYSIS_PERIOD in the json and when reading this in the plot operator, it fills this with the appropriate environment value?