Blender Git Loki

Two small fixes:

- "Add node" was showing on wrong location when used via pulldown menus.
Now this option will put the nodes in center of the view.

- The Curves widget was making itself smaller/bigger based on width of region.
That messes up the layout engine now - especially the code that checks if
there's a scroller needed or not (it went into an eternal feedback loop).

Now this widget has fixed height (like the other larger widgets).

Better would be to allow such large widgets to be scaled vertically individually.
That's for the todo!