Cover Image - First and tests (#170)

* Changed how natural sort works to cover more cases

* Changed the name of CoverImage regex for Parser and added more cases.

* Changed how we get result from Task.Run()

* Defer execution of a loop till we really need it and added another TODO for later this iteration.

* Big refactor to cover image code to unify between IOCompression and SharpCompress. Both use methods to find the correct file. This results in one extra loop through entries, but simplifies code signficantly.

In addition, new unit tests for the methods that actually do the logic on choosing cover file and first file.

* Removed dead code

* Added missing doc

API/Data/LibraryRepository.cs

@@ -92,6 +92,7 @@ namespace API.Data
         /// <returns></returns>
         public async Task<Library> GetFullLibraryForIdAsync(int libraryId)
         {
+            
             return await _context.Library
                 .Where(x => x.Id == libraryId)
                 .Include(f => f.Folders)