format_means_df()
fround_x() helpers for more consistent
formatting, especially for Lancetformat_means_df() to
format_metric_cols(), with arg name change from
central_var to var_prefixcran initial submit harmonization
mag override can now be passed down from user API
added rate-space metric/metric
Internal state management improvements. No changes to user interface.
Ready for CRAN submission.
All tests passing.