Fixes missing IF/ELSE brace (PSR standards)
Moved the inline authentication check method (for where Filters just aren't granular enough) into the BaseController, updated the Version model to include 'notes' as a fillable field.
Adds new migration to add the download_url column for versions.
Implements the new download URL functionality as logged in issue #10 (https://github.com/SIMSBulkImport/WebAPI/issues/10)