added challenge main screen (just testing)

VocaluxeLib/PartyModes/IPartyMode.cs

@@ -53,8 +53,9 @@ namespace Vocaluxe.PartyModes
     {
         bool Init(string Folder);
         void Initialize(Basic Base);
+        void AddScreen(CMenuParty Screen, string ScreenName);
 
-        CMenu GetNextPartyScreen();
+        CMenuParty GetNextPartyScreen();
         EScreens GetStartScreen();
         EScreens GetMainScreen();
         ScreenSongOptions GetScreenSongOptions();