Tech Debt + Series Sort bugfix (#1192)

* Code cleanup.

When copying files, if the target file already exists, append (1), (2), etc onto the file (this is enhancing existing implementation to allow multiple numbers)

* Added a ton of null checks to UpdateSeriesMetadata and made the code work on the rare case (not really possible) that SeriesMetadata doesn't exist.

* Updated Genre code to use strings to ensure a better, more fault tolerant update experience.

* More cleanup on the codebase

* Fixed a bug where Series SortName was getting emptied on file scan

* Fixed a bad copy

* Fixed unit tests

API/Data/Repositories/SeriesRepository.cs

@@ -378,7 +378,7 @@ public class SeriesRepository : ISeriesRepository
 
 
     /// <summary>
-    /// Returns Volumes, Metadata, and Collection Tags
+    /// Returns Volumes, Metadata (Incl Genres and People), and Collection Tags
     /// </summary>
     /// <param name="seriesId"></param>
     /// <returns></returns>