GtkBuilder: Emit a more detailed error for templates
GtkBuilder: Emit a more detailed error for templates

Add the class and parent class name to the error message.
gtk-builder-tool will parse the error message and use the
class names for trying again to parse the file as a template.

jadahl/gtk,jigpu/gtk,chergert/gtk,grubersjoe/adwaita,Adamovskiy/gtk,davidgumberg/gtk,davidgumberg/gtk,Adamovskiy/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,alexlarsson/gtk,Adamovskiy/gtk,alexlarsson/gtk,davidgumberg/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jigpu/gtk,chergert/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jigpu/gtk,grubersjoe/adwaita,alexlarsson/gtk,davidgumberg/gtk,grubersjoe/adwaita,grubersjoe/adwaita,jigpu/gtk,grubersjoe/adwaita,chergert/gtk,jigpu/gtk,alexlarsson/gtk,jigpu/gtk,alexlarsson/gtk,grubersjoe/adwaita,chergert/gtk,jigpu/gtk,chergert/gtk,alexlarsson/gtk,davidgumberg/gtk,jadahl/gtk,jigpu/gtk,alexlarsson/gtk,Adamovskiy/gtk,alexlarsson/gtk,jadahl/gtk,jadahl/gtk,Adamovskiy/gtk,chergert/gtk,jadahl/gtk,chergert/gtk,jadahl/gtk,Adamovskiy/gtk,davidgumberg/gtk,davidgumberg/gtk,jadahl/gtk