Add an 'About' dialog for the Qt UI

The dialog is similar to the one in the GTK version

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

qt-ui/about.h

@@ -0,0 +1,26 @@
+#ifndef ABOUT_H
+#define ABOUT_H
+
+#include <QDialog>
+#include <QPushButton>
+
+namespace Ui {
+	class SubsurfaceAbout;
+}
+
+class SubsurfaceAbout : public QDialog {
+	Q_OBJECT
+
+public:
+	static SubsurfaceAbout* instance();
+private slots:
+	void licenseClicked();
+	void websiteClicked();
+private:
+	explicit SubsurfaceAbout(QWidget* parent = 0, Qt::WindowFlags f = 0);
+	QPushButton *licenseButton;
+	QPushButton *websiteButton;
+	Ui::SubsurfaceAbout *ui;
+};
+
+#endif