[Banshee-List] Smooth (kinetic) scroll enabled by default

[Gabriel Burt <gabriel burt gmail com>]

Hi Banshees,

I just enabled smooth scroll in trunk by default.  You used to be able
to enable it with --smooth-scroll; now you can disable it with
--no-smooth-scroll.  You'll notice the difference when you use the
mouse wheel to scroll - if you click the scroll arrows or drag the
scrollbar, it jumps immediately as it did before.

The algorithm can certainly be tweaked;  feel free to adjust it in
src/Libraries/Hyena.Gui/Hyena.Widgets/SmoothScrolledWindow.cs and file
bugs with patches.

Note that this only applies to our ListView widgets
(track/artist/album etc lists, not the source list) - though you might
be able to rework SmoothScrolledWindow into a SmoothScrollAdapter
class that can modify the behavior of any widget with an Adjustment
and a ScrollEvent; that would be very cool.

Thanks!

Gabriel