Winforms Example Supports Tabbed Browsing

Made some changes a few months ago to make the WinForms Example support tabs, I've just merged in the changes from `master` and here they are.

It's fairly basic at this stage. Had a few problems with the WinForms tabcontrol which aren't totally resolved. So if anyone out there has experience with `DockStyle.Fill` and the problems with TabControls then please submit your ideas.