1. Refactor to make code better testable (move columns and view source to `files_views` folder)
2. Fix deletion time fallback (JS Date vs unix timestamp for
"delted"-column)
3. Correctly sort `deletedBy` and `originalLocation` columns to use
natural sort like any other column
4. Add unit tests for columns and views
Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>