Added support for Warnings and RuntimeInformation

Added Warnings and RuntimeInformation to standard QueryPlanNode structure. Added this data to HTML pane.
Modified how OutputList content is rendered. Can deal with different configurations of col references now.
Added hot key, F6, for switching between tree view and HTML pane.
Stopped HTML pane being written to every Key Up event.

Now only updates if the selected node is different.
Added a raw XML view mode to allow users to explore the actual sqlplan file.
Added depth level and percent CPU and IO to each node label.