Remove ScrollView control, add a Change event to the DrawingArea control, and propagate MouseWheel events automatically.

[GB.GTK]
* NEW: ScrollView: Remove ScrollView control.
* NEW: DrawingArea: Change is a new event that is raised when the Application.Animations or Application.Shadows property changes.
* NEW: MouseWheel events are now automatically propagated to the parent control if they are not handled by the child.
* BUG: ScrollBar: Correctly raise the Change event in all cases.
* BUG: Slider: Correctly raise the Change event in all cases.

[GB.GTK3]
* NEW: ScrollView: Remove ScrollView control.
* NEW: DrawingArea: Change is a new event that is raised when the Application.Animations or Application.Shadows property changes.
* NEW: MouseWheel events are now automatically propagated to the parent control if they are not handled by the child.
* BUG: ScrollBar: Correctly raise the Change event in all cases.
* BUG: Slider: Correctly raise the Change event in all cases.