Remove redundant code

1. remove this
2. auto property should be only 1 line
3. misc
4. part of refactoring for PR #494

Wox/ResultListBox.xaml.cs

@@ -19,7 +19,7 @@ namespace Wox
     {
         public void AddResults(List<Result> newResults, string resultId)
         {
-            var vm = this.DataContext as ResultsViewModel;
+            var vm = DataContext as ResultsViewModel;
             vm.AddResults(newResults, resultId);
         }