Introducing Maximum & Minimum properties to Slider control

This commit introduces `Maximum` & `Minimum` properties to the `Slider` control. 

Before this commit, there was no way to get the maximum value for a Slider control. Because of this, it is not easy to slide to the end from a test because we don't know when to stop calling `LargeIncrementButton.Click()`.

With this in place, we can write the following from a test to slide to the end

```csharp
var t = window.Get<Slider>(SearchCriteria.ByAutomationId("slider1"));
while (t.Value < t.Maximum)
{
      t.LargeIncrementButton.Click(); 
}
```