add CListHelpers class

this can be used to factor out duplicate code implementations
from all the various channel-, bouquet-, eventlists etc...

src/gui/widget/listhelpers.h

@@ -0,0 +1,30 @@
+/*
+	Helper functions for various list implementations in neutrino
+	Copyright (C) 2016 Stefan Seyfried
+
+	License: GPL
+
+	This program is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with this program; if not, see http://www.gnu.org/licenses/
+*/
+
+
+#ifndef __LISTHELPERS__
+#define __LISTHELPERS__
+
+class CListHelpers
+{
+	public:
+		template <class T> int UpDownKey(T list, neutrino_msg_t k, int lines, int sel);
+};
+#endif