[Enhancement] Expander: Add common animation configuration properties + touch capture view property

[AndreiMisiukevich]

Summary

• It should be possible to set animation length/easing for both expanding/collapsing animation in one place.
• It should be possible to define the view that triggers animation when tapped. (Now the animation is starting by tapping over the entire header)

API Changes

Add:

• uint Expander.AnimationLength { get; set; }
• Easing Expander.AnimationEasing { get; set; }
• View Expander.TouchCaptureView { get; set; }

Intended Use Case

• I guess everyone agrees that setting animation once is more convenient than twice (if I want to change the animation length from 250 ms to 200).
• Sometimes it's necessary to set the "clickable" area to some view (this view can be outside of expander, but it controls the state)

Who Will Do The Work?

• I am willing to take this on myself
• Just putting this out there for someone to pick up