Use the normal test helper for case_study_row_test.rb

This relies on a bunch of real-db stuff like 
factorygirl and some activesupport stuff.

It's only passing on jenkins because the normal 
test helper gets loaded regardless in the bulk 
rake task.
Bring statistical_data_set in line with other rows

Should use document_collection_{1-4} rather than
data_collection as a CSV entry.
Case study row should list collection slugs.

Not collections themselves.