WIP Clinic Exporter

Exports all clinic data to various formats

TODO

- Implement `to_xlsx`, `to_json`, and `to_csv`
- Wrap exported data in some kind of presenter so it's less messy
- Wire up to the UI so clinic organizers can use it
Fix documentation errors and add supported data types

Eventually we will want to list the supported data types somewhere in
the UI. For now I've created a constant which lists every type the
exporter can work with. I also use it as the default when no data_types
are provided.

I also updated some out of date documentation :anguished:
Format for exported data

Playing with a YAML file to map column names to model attributes
Improvements based on @rmascarenhas's suggestions
Add procedures format for Clinic Export

Support associated records in ClinicExport#data via the new column
method (See docs for details)
Prescription, PreMed, and Survey formats for ClinicExporter
Export clinic data button

Taking the axlsx_rails gem for a test drive. So far so good. Exports all
of the clinic data (via ClinicExporter) to an xlsx file
Fix Chart # in format file
Merge branch 'export-data'