Generates a list of functions that are used to subset the
processed ManyEcoEvo dataset (e.g.data(ManyEcoEvo_results) containing
out-of-sample predictions $y_i$.
Details
The subset functions are used to filter out predictions that are not to be included in the meta-analysis.
See also
Other Utility functions: 
%nin%(),
capwords(),
named_group_split(),
rm_inf_na(),
subset_fns_Zr()
