enable plex for television (#73)

* add plex show, season sync

* sync plex episodes

* sync plex episode statistics

* update plex artwork as needed

* code cleanup

* add note about tests

ErsatzTV.Core/Scheduling/PlayoutBuilder.cs

@@ -13,6 +13,8 @@ using Map = LanguageExt.Map;
 
 namespace ErsatzTV.Core.Scheduling
 {
+    // TODO: these tests fail on days when offset changes
+    // because the change happens during the playout
     public class PlayoutBuilder : IPlayoutBuilder
     {
         private static readonly Random Random = new();