Go back to last target button

[gah5118]

It would be great to have a button on the bar to quickly go back to the last selected target. this would be useful when working back and forth with materials. lately, I'd be in a node graph looking at the material ball, then have to go back to the top graph or the sidebar to hit the render target to see how it is looking on the object. rinse and repeat until finished.

In other words, ideally, we should be able to be working in any graph, selecting material views, then click the "goback" button to see the last render target or object we were using.

Hope that made sense!
Thanks!