Implemented the ability to allow the admin to change the cover generation size. (#2213)

Changed how covers are merged together. Now a cover image will always be generated for reading list and collections.

Fixed reading list page being a bit laggy due to a missing trackby function.

Reading list page will now show the cover image always. Collection detail page will only hide the image if there is no summary on the collection.

API/Services/MediaErrorService.cs

@@ -37,6 +37,7 @@ public class MediaErrorService : IMediaErrorService
 
     public void ReportMediaIssue(string filename, MediaErrorProducer producer, string errorMessage, Exception ex)
     {
+        // TODO: Localize all these messages
         // To avoid overhead on commits, do async. We don't need to wait.
         BackgroundJob.Enqueue(() => ReportMediaIssueAsync(filename, producer, errorMessage, ex.Message));
     }