* Remove file_path_for, cropped_file_url (dead code)
* Remove complete_preview_file_url (preview_file_url now returns absolute links)
* Remove `file_name` (only used for Download link in sidebar)
The Rails convention is for test/helpers to be used for testing the view
helpers in app/helpers. We were using it to store certain utility
methods instead. Move these to test/test_helpers so that test/helpers
can be used for its intended purpose.
