feat: #3209 #3328 add win10 and fluent TextBox styles

- Add new attached property ControlsHelper.DisabledBorderBrush
- Add new TextBox style values
  - TextControlBorderThemeThickness
  - TextControlThemePadding
  - TextControlBorderThemeThicknessFocused
  - TextControlPlaceholderMargin
- Add new Win10 style: MahApps.Styles.TextBox.Win10
- Add new Fluent style: MahApps.Styles.TextBox.Fluent
- Add new brushes:
  - MahApps.Brushes.TextControl.Background
  - MahApps.Brushes.TextControl.BackgroundPointerOver
  - MahApps.Brushes.TextControl.BackgroundFocused
  - MahApps.Brushes.TextControl.BackgroundDisabled
  - MahApps.Brushes.TextControl.BorderBrush
  - MahApps.Brushes.TextControl.BorderBrushPointerOver
  - MahApps.Brushes.TextControl.BorderBrushFocused
  - MahApps.Brushes.TextControl.BorderBrushDisabled
  - MahApps.Brushes.TextControl.Foreground
  - MahApps.Brushes.TextControl.ForegroundPointerOver
  - MahApps.Brushes.TextControl.ForegroundFocused
  - MahApps.Brushes.TextControl.ForegroundDisabled
  - MahApps.Brushes.TextControl.PlaceholderForeground
  - MahApps.Brushes.TextControl.PlaceholderForegroundPointerOver
  - MahApps.Brushes.TextControl.PlaceholderForegroundFocused
  - MahApps.Brushes.TextControl.PlaceholderForegroundDisabled
  - MahApps.Brushes.TextControl.HeaderForeground
  - MahApps.Brushes.TextControl.HeaderForegroundDisabled
  - MahApps.Brushes.TextControl.SelectionHighlightColor
  - MahApps.Brushes.TextControl.ButtonBackground
  - MahApps.Brushes.TextControl.ButtonBackgroundPointerOver
  - MahApps.Brushes.TextControl.ButtonBackgroundPressed
  - MahApps.Brushes.TextControl.ButtonBorderBrush
  - MahApps.Brushes.TextControl.ButtonBorderBrushPointerOver
  - MahApps.Brushes.TextControl.ButtonBorderBrushPressed
  - MahApps.Brushes.TextControl.ButtonForeground
  - MahApps.Brushes.TextControl.ButtonForegroundPointerOver
  - MahApps.Brushes.TextControl.ButtonForegroundPressed

BREAKING CHANGE: change background for dark theme

Change the dark theme background from #FF252525 to #FF141414.

src/MahApps.Metro/Controls/Helper/ControlsHelper.cs

@@ -223,6 +223,43 @@ public static void SetMouseOverBorderBrush(DependencyObject obj, Brush value)
             obj.SetValue(MouseOverBorderBrushProperty, value);
         }
 
+        public static readonly DependencyProperty DisabledBorderBrushProperty
+            = DependencyProperty.RegisterAttached(
+                "DisabledBorderBrush",
+                typeof(Brush),
+                typeof(ControlsHelper),
+                new FrameworkPropertyMetadata(Brushes.Transparent, FrameworkPropertyMetadataOptions.AffectsRender | FrameworkPropertyMetadataOptions.Inherits));
+
+        /// <summary>
+        /// Gets the brush used to draw the disabled border brush.
+        /// </summary>
+        [Category(AppName.MahApps)]
+        [AttachedPropertyBrowsableForType(typeof(TextBox))]
+        [AttachedPropertyBrowsableForType(typeof(CheckBox))]
+        [AttachedPropertyBrowsableForType(typeof(RadioButton))]
+        [AttachedPropertyBrowsableForType(typeof(DatePicker))]
+        [AttachedPropertyBrowsableForType(typeof(ComboBox))]
+        [AttachedPropertyBrowsableForType(typeof(Tile))]
+        public static Brush GetDisabledBorderBrush(DependencyObject obj)
+        {
+            return (Brush)obj.GetValue(DisabledBorderBrushProperty);
+        }
+
+        /// <summary>
+        /// Sets the brush used to draw the disabled border brush.
+        /// </summary>
+        [Category(AppName.MahApps)]
+        [AttachedPropertyBrowsableForType(typeof(TextBox))]
+        [AttachedPropertyBrowsableForType(typeof(CheckBox))]
+        [AttachedPropertyBrowsableForType(typeof(RadioButton))]
+        [AttachedPropertyBrowsableForType(typeof(DatePicker))]
+        [AttachedPropertyBrowsableForType(typeof(ComboBox))]
+        [AttachedPropertyBrowsableForType(typeof(Tile))]
+        public static void SetDisabledBorderBrush(DependencyObject obj, Brush value)
+        {
+            obj.SetValue(DisabledBorderBrushProperty, value);
+        }
+
         /// <summary>
         /// DependencyProperty for <see cref="CornerRadius" /> property.
         /// </summary>