More modernization

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

Application/FeedParsers/AtomParser.cs

@@ -1,5 +1,5 @@
-using System;
-using Common.Debug;
+using Serilog;
+using System;
 using System.Xml;
 
 namespace FeedCenter.FeedParsers
@@ -68,7 +68,7 @@ namespace FeedCenter.FeedParsers
             }
             catch (XmlException xmlException)
             {
-                Tracer.WriteLine("XML error: " + xmlException.Message + "\n" + feedText);
+                Log.Logger.Error(xmlException, "Exception: {0}", feedText);
 
                 return FeedReadResult.InvalidXml;
             }