Updated all the TODO: comments in the Umbraco.Core project so they are all in the same format. ( // TODO: ) (#4220)

Also moved some of the comments so they are will work better / are not within Code Documentation comments

src/Umbraco.Core/Services/Implement/NotificationService.cs

@@ -307,7 +307,7 @@ namespace Umbraco.Core.Services.Implement
                     summary.Append("<table style=\"width: 100 %; \">");
                     foreach (var p in content.Properties)
                     {
-                        //todo doesn't take into account variants
+                        // TODO: doesn't take into account variants
 
                         var newText = p.GetValue() != null ? p.GetValue().ToString() : "";
                         var oldText = newText;