Implement About Dialog

Prepared XDG icon theme in :/icons/multimc. will only be usefull as soon
as Qt decides to support custom fallback themes. use the resources
directly for now.

gui/aboutdialog.h

@@ -0,0 +1,22 @@
+#ifndef ABOUTDIALOG_H
+#define ABOUTDIALOG_H
+
+#include <QDialog>
+
+namespace Ui {
+class AboutDialog;
+}
+
+class AboutDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    explicit AboutDialog(QWidget *parent = 0);
+    ~AboutDialog();
+
+private:
+    Ui::AboutDialog *ui;
+};
+
+#endif // ABOUTDIALOG_H