[TabPane] Support for draggable tabs

By default when you create a TabPane, I don't think it provides the best out the box experience.

I've already filed a ticket about the close animation (RT-17906) but there is more than that. I think the default style should be better (shape and close button style). I also think you should be able to rearrange tabs by default (or by setting a property allowing it). I also think that there should be a "new tab" button by default (that obviously can be listened to) that again, can be made visible or not.

You only need to look at any modern browser to see what I'm talking about - my favourite is chrome and if the TabPane looked and behaved like that by default, I would be very happy.