Use DataTemplate in RangeSlider instead of a Converter (AutoToolTipContentTemplate)

[Anapher]

I know, I did implemented the DependencyProperty AutoToolTipTextConverter in #1833 but I think a DataTemplate would fit much better because of obvious reasons: No need to write a new IValueConverter for every RangeSlider, more possiblities (coloring, font, icons, etc.) and it's the default in WPF.

It was fairly complicated to implement that (because two values are displayed when moving the range and I didn't want to change the default behavior) but I think it works pretty good. Here is a small example about how to use it:

                    <Controls:RangeSlider [...]>
                        <Controls:RangeSlider.AutoToolTipContentTemplate>
                            <DataTemplate>
                                <TextBlock>
                                    <Run Foreground="Red" Text="{Binding Mode=OneWay, StringFormat=#.00}" />
                                    <Run Text="Punks" />
                                </TextBlock>
                            </DataTemplate>
                        </Controls:RangeSlider.AutoToolTipContentTemplate>
                    </Controls:RangeSlider>

Result: