Allow open settings from main window context menu, fix #519

Wox/MainWindow.xaml

@@ -36,7 +36,17 @@
                      Text="{Binding QueryText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                      PreviewDragOver="OnPreviewDragOver"
                      AllowDrop="True"
-                     x:Name="QueryTextBox" />
+                     x:Name="QueryTextBox">
+                <TextBox.ContextMenu>
+                    <ContextMenu>
+                        <MenuItem Command="ApplicationCommands.Cut"/>
+                        <MenuItem Command="ApplicationCommands.Copy"/>
+                        <MenuItem Command="ApplicationCommands.Paste"/>
+                        <Separator />
+                        <MenuItem Header="Settings" Click="OnContextMenusForSettingsClick" />
+                    </ContextMenu>
+                </TextBox.ContextMenu>
+            </TextBox>
             <Line x:Name="ProgressBar" HorizontalAlignment="Right"
                   Style="{DynamicResource PendingLineStyle}" Visibility="{Binding ProgressBarVisibility, Mode=TwoWay}" 
                   Y1="0" Y2="0" X2="100" Height="2" Width="752" StrokeThickness="1">

Wox/MainWindow.xaml.cs

@@ -366,5 +366,10 @@ namespace Wox
         {
             e.Handled = true;
         }
+
+        private void OnContextMenusForSettingsClick(object sender, RoutedEventArgs e)
+        {
+            App.API.OpenSettingDialog();
+        }
     }
 }

Wox/ViewModel/MainViewModel.cs

@@ -22,7 +22,6 @@ namespace Wox.ViewModel
     {
         #region Private Fields
 
-        private bool _isProgressBarTooltipVisible;
         private double _left;
         private double _top;