Dataset files view - Show (table), Delete

[langphil]

Dataset collections are home to dataset files - these files should be viewable by publishers whilst in a prepublished state. Currently these views are being created with Github Pages / Jekyll.

• Create new routes for 'show' and 'delete'
• Create new view for displaying the S3 csv data table
• Add links to the 'dataset collection' view in the relevant tables under the 'dropdown' element.