Fix hc:TextBox disabled opacity.

[GF-Huang]

值得一提的是，下图中的 before 一侧，文本框的边框变得几乎不可见了，这是由于同时设置了父元素 root 和子元素 border 的 opacity 为 0.4 导致的，这使得 border 的 opacity 变为 0.16 (0.4*0.4).

HandyControl/src/Shared/HandyControl_Shared/Themes/Styles/Base/TextBoxBaseStyle.xaml

Lines 139 to 154 in 4146ee5

	<Grid x:Name="root" Grid.Row="1">
	<Grid.ColumnDefinitions>
	<ColumnDefinition />
	<ColumnDefinition Width="Auto" />
	</Grid.ColumnDefinitions>
	<Border x:Name="border" Grid.ColumnSpan="2" CornerRadius="{Binding Path=(hc:BorderElement.CornerRadius),RelativeSource={RelativeSource TemplatedParent}}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" />
	<TextBlock VerticalAlignment="{TemplateBinding VerticalContentAlignment}" Margin="{TemplateBinding Padding}" Visibility="{TemplateBinding Text,Converter={StaticResource String2VisibilityReConverter}}" HorizontalAlignment="Stretch" Style="{StaticResource TextBlockDefaultThiLight}" Text="{Binding Path=(hc:InfoElement.Placeholder),RelativeSource={RelativeSource TemplatedParent}}"/>
	<ScrollViewer Margin="-2,0,0,0" Grid.Column="0" Padding="{TemplateBinding Padding}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" x:Name="PART_ContentHost" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
	<Button Height="Auto" Width="Auto" HorizontalContentAlignment="Left" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" hc:IconElement.Width="14" Command="interactivity:ControlCommands.Clear" Visibility="Collapsed" Name="ButtonClear" Grid.Column="1" Style="{StaticResource ButtonIcon}" Padding="{Binding Padding, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource ThicknessSplitConverter}, ConverterParameter='0,0,1,0'}" hc:IconElement.Geometry="{StaticResource DeleteFillCircleGeometry}" Foreground="{Binding BorderBrush,ElementName=border}" />
	</Grid>
	</Grid>
	<ControlTemplate.Triggers>
	<Trigger Property="IsEnabled" Value="false">
	<Setter Property="Opacity" TargetName="border" Value="0.4"/>
	<Setter Property="Opacity" TargetName="root" Value="0.4"/>
	</Trigger>