support multi-episode files in local libraries (#240)

* add unused episode nfo reader

* move episode number from episode to episode metadata

* first pass at loading multi-episode metadata from nfo files

* fix episode scanning

* local multi-part episode fixes

* code cleanup

ErsatzTV.Infrastructure/Jellyfin/JellyfinApiClient.cs

@@ -568,11 +568,6 @@ namespace ErsatzTV.Infrastructure.Jellyfin
                     EpisodeMetadata = new List<EpisodeMetadata> { metadata }
                 };
 
-                if (item.IndexNumber.HasValue)
-                {
-                    episode.EpisodeNumber = item.IndexNumber.Value;
-                }
-
                 return episode;
             }
             catch (Exception ex)
@@ -605,6 +600,11 @@ namespace ErsatzTV.Infrastructure.Jellyfin
                 Writers = Optional(item.People).Flatten().Collect(r => ProjectToWriter(r)).ToList()
             };
 
+            if (item.IndexNumber.HasValue)
+            {
+                metadata.EpisodeNumber = item.IndexNumber.Value;
+            }
+
             if (DateTime.TryParse(item.PremiereDate, out DateTime releaseDate))
             {
                 metadata.ReleaseDate = releaseDate;