Add built-in (inertial) manipulation via dep. properties

[erodewald]

Simple implementation that allows your "swipes" to translate, rotate, or zoom the attached UIElement.

ScrollViewer supports translation of the HorizontalOffset and VerticalOffset properties. Arbitrary UIElements support rotate, zoom, and translate with inertial movement (it will keep moving after you let off the screen).

[erodewald]

Refers to issue #8