Version filtering and general related code sanitization.

Version list dialog has alternating row background set.
Nostalgia versions, based on OneSix.

backend/NostalgiaInstance.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "OneSixInstance.h"
+
+class LIBMULTIMC_EXPORT NostalgiaInstance : public OneSixInstance
+{
+	Q_OBJECT
+public:
+	explicit NostalgiaInstance(const QString &rootDir, SettingsObject * settings, QObject *parent = 0);
+};