Implement a common Interface for all MenuElements

Also remove CSongMenu and replace it with a factory class

VocaluxeLib/Menu/SongMenu/CSongMenuList.cs

@@ -1,44 +0,0 @@
-#region license
-// This file is part of Vocaluxe.
-// 
-// Vocaluxe 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 3 of the License, or
-// (at your option) any later version.
-// 
-// Vocaluxe 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 Vocaluxe. If not, see <http://www.gnu.org/licenses/>.
-#endregion
-
-using VocaluxeLib.PartyModes;
-
-namespace VocaluxeLib.Menu.SongMenu
-{
-    class CSongMenuList : CSongMenuFramework
-    {
-        public CSongMenuList(int partyModeID)
-            : base(partyModeID) {}
-
-        public override float SelectedTileZoomFactor
-        {
-            get { return 1.2f; }
-        }
-
-        public override bool HandleInput(ref SKeyEvent keyEvent, SScreenSongOptions options)
-        {
-            return false;
-        }
-
-        public override bool HandleMouse(ref SMouseEvent mouseEvent, SScreenSongOptions songOptions) { return false; }
-
-        public override CStatic GetSelectedSongCover()
-        {
-            return null;
-        }
-    }
-}