Add the ability to export print template as html

This way we can view the html generated from a print template, for
debugging, validation or printing via your favorite browser.

Signed-off-by: Anton Lundin <glance@acc.umu.se>

desktop-widgets/printdialog.h

@@ -33,6 +33,7 @@ private
 slots:
 	void onFinished();
 	void previewClicked();
+	void exportHtmlClicked();
 	void printClicked();
 	void onPaintRequested(QPrinter *);
 	void createPrinterObj();