More modernization

- Split generic "common" libraries into specific libraries
- Use other packages in lieu of custom code
- General cleanup

Application/MainWindow/CategoryList.cs

@@ -1,12 +1,12 @@
-using System;
+using FeedCenter.Properties;
+using System;
 using System.Linq;
 using System.Windows;
 using System.Windows.Controls;
-using FeedCenter.Properties;
 
 namespace FeedCenter
 {
-    public partial class MainWindow : IDisposable
+    public partial class MainWindow
     {
         private void DisplayCategory()
         {
@@ -96,12 +96,5 @@ namespace FeedCenter
 
             Settings.Default.LastCategoryID = _currentCategory?.Id.ToString() ?? string.Empty;
         }
-
-        public void Dispose()
-        {
-            _mainTimer?.Dispose();
-            _feedReadWorker?.Dispose();
-            _commandLineListener?.Dispose();
-        }
     }
-}
+}