Add initial admin CSV export for Papers, Users

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Humanize CSV column headers

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Improve AdminController#build_csv variable names

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Merge pull request #2 from eurucamp/export-csv

Export CSV