Adds margin to TreeListView content

Adds a margin to the TreeListView's content presenter to improve spacing.

Author: Keboo

src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.ListView.xaml

@@ -193,8 +193,6 @@
     </Style.Triggers>
   </Style>
 
-
-
   <Style x:Key="MaterialDesignListView" TargetType="{x:Type ListView}">
     <Style.Resources>
       <converters:ListViewGridViewConverter x:Key="MaterialDesignListViewItemContainerStyleConverter"

src/MaterialDesignThemes.Wpf/TreeListView.cs

@@ -324,6 +324,7 @@ private DataTemplate CreateToggleButtonTemplate(DataTemplate originalTemplate)
         if (originalTemplate != null)
         {
             var originalContentFactory = new FrameworkElementFactory(typeof(ContentPresenter));
+            originalContentFactory.SetValue(ContentPresenter.MarginProperty, new Thickness(8, 0, 0, 0));
             originalContentFactory.SetValue(ContentPresenter.ContentTemplateProperty, originalTemplate);
             stackPanelFactory.AppendChild(originalContentFactory);
         }