Be able to group user-defined functions into folders

[Kenneth-Barber]

Measures can be associated with tables and can be organized further into folders. User-defined functions currently cannot be organized in either of these ways, and so all functions in the entire file are in 1 place in alphabetical order. The current workaround is to add prefixes to the function name so that functions with the same prefixes will appear together in the alphabetically sorted list.