Add storage for manually-entered tasks that can be retained by the vote

counter, and not lost between Manage Votes window loads.
Added at the Tally level so that it's not reset by just changing partitioning.

TallyCore/Tally.cs

@@ -21,6 +21,8 @@ public class Tally : INotifyPropertyChanged
         IQuest lastTallyQuest = null;
         List<HtmlDocument> loadedPages = null;
 
+        public HashSet<string> ManualTasks { get; } = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
         public Tally()
             : this(null, null)
         {
@@ -125,6 +127,7 @@ public async Task Run(IQuest quest, CancellationToken token)
 
                 TallyResults = string.Empty;
                 lastTallyQuest = quest;
+                ManualTasks.Clear();
 
                 var fa = await quest.GetForumAdapterAsync(token);