Search TextBlock horizontal alignment centered

Hi @aosyatnik, there is no immediate need for updating this, but sometimes we keep the length of line short by doing the following (bringing ```Binding``` statement under an attribute to make it shorter, like this:

```xml
<TextBlock FontSize="14"
           Text="Search">
    <TextBlock.Visibility>
        <Binding Path="SearchText"
                 Converter="{StaticResource NonEmptyStringToCollapsedConverter}" />
    </TextBlock.Visibility>
</TextBlock>
```