Reorder blocks, widgets within left pane

[wayfaringrob]

It would be super handy if I could drag or otherwise reorder items from the left pane rather than on the page. It's a bit of a pain to drag stuff in the page itself - the handles for the right thing can be hard to get at, and the page doesn't scroll with you. It would also be intuitive and consistent with other applications, including Esri applications.