Add function that checks HUD_specs and returns values based on reference numbers

[kiadso]

Since in the bulk of our HMIS code, we are working with the Reference Nos that are indicated in the HUD CSV Export specs but we don't want those numbers to show in final reporting, it would be good to have a function that just takes any data element and value and returns its value, as according to this document (which changes every couple of years) https://github.com/COHHIO/COHHIO_HMIS/blob/Development/public_data/HUDSpecs.csv

https://colinfay.me/tidyeval-1/ is a good place to pick up where I left off