title: Tab is focusing on my implicitly generated ListBoxItem
body: <p>I have a ListBox that hosts controls.  I would like to be able to tab from one control to a control the next row down.  It appears that the implicitly generated ListBoxItem is getting focus after I hit tab.  How can I get around this ? </p>
  
  <pre><code>&lt;ListBox ItemsSource="{Binding UiControls}" 
           DockPanel.Dock="Top"
           BorderThickness="0"
           Background="{DynamicResource ControlInteriorBrush}"
           KeyboardNavigation.TabNavigation="Continue"
           KeyboardNavigation.ControlTabNavigation="Continue"&gt;
      &lt;ListBox.ItemTemplate&gt;
          &lt;DataTemplate&gt;
              &lt;Grid&gt;
                  &lt;Grid.ColumnDefinitions&gt;
                      &lt;ColumnDefinition Width="Auto" SharedSizeGroup="col1"/&gt;
                      &lt;ColumnDefinition Width="Auto" SharedSizeGroup="col2"/&gt;
                      &lt;ColumnDefinition Width="Auto" SharedSizeGroup="col3"/&gt;
                  &lt;/Grid.ColumnDefinitions&gt;
                  &lt;Border Grid.Column="0"&gt;
                      &lt;TextBlock Text="{Binding Path=Label}" 
                                 FontWeight="Bold"
                                 VerticalAlignment="Center"     
                                 Background="{DynamicResource ControlInteriorBrush}"
                                 Foreground="{DynamicResource FontBrush}"
                                 Margin="0,0,25,0"
                                 KeyboardNavigation.TabNavigation="Continue"/&gt;
                  &lt;/Border&gt;
                  &lt;Controls:AutoCompleteTextBox Default="{Binding Path=DefaultValue}"  
                                                Items="{Binding Path=DropDownValues}"
                                                Tag="{Binding}"
                                                DataContext="{Binding}"
                                                Width="300" 
                                                Grid.Column="1" 
                                                Height="30"
                                                Background="{DynamicResource ControlInteriorBrush}"
                                                Margin="0,0,10,0"
                                                KeyboardNavigation.IsTabStop="True"
                                                FocusManager.IsFocusScope="True"/&gt;
              &lt;/Grid&gt;
          &lt;/DataTemplate&gt;
      &lt;/ListBox.ItemTemplate&gt;
  &lt;/ListBox&gt;
  </code></pre>