Add DataTemplates for range slider auto tool tip values

[punker76]

Describe the changes you have made to improve this project

Remove AutoToolTipTextConverter and add new properties to allow setting a DataTemplate for the AutoToolTip values (AutoToolTipLowerValueTemplate, AutoToolTipUpperValueTemplate, AutoToolTipRangeValuesTemplate)

Introduce also a helper class RangeSliderAutoTooltipValues which is used as the ToolTip content for the AutoToolTipRangeValuesTemplate.

Example

<Controls:RangeSlider Width="200"
                      Margin="4"
                      Controls:SliderHelper.ChangeValueBy="LargeChange"
                      Controls:SliderHelper.EnableMouseWheel="MouseHover"
                      AutoToolTipPlacement="TopLeft"
                      LargeChange="10"
                      LowerValue="40"
                      Maximum="100"
                      Minimum="0"
                      Orientation="Horizontal"
                      SmallChange="1"
                      Style="{DynamicResource MahApps.Metro.Styles.RangeSlider.Win10}"
                      UpperValue="60">
    <Controls:RangeSlider.AutoToolTipRangeValuesTemplate>
        <DataTemplate DataType="Controls:RangeSliderAutoTooltipValues">
            <UniformGrid Columns="2" Rows="2">
                <TextBlock Text="From:" HorizontalAlignment="Right" />
                <TextBlock Text="{Binding LowerValue, StringFormat='{}{0:N2}'}" HorizontalAlignment="Right" />
                <TextBlock Text="To:" HorizontalAlignment="Right" />
                <TextBlock Text="{Binding UpperValue, StringFormat='{}{0:N2}'}" HorizontalAlignment="Right" />
            </UniformGrid>
        </DataTemplate>
    </Controls:RangeSlider.AutoToolTipRangeValuesTemplate>
</Controls:RangeSlider>

Additional context

Original idea by this PR #2784 is from @Anapher

Closed Issues

Closes #2784