Added Dancing Stage 3DDX (SINGLE MODE ONLY)

NOTE: I commented out an ASSERT in NoteData.cpp
at Line 429
//	ASSERT( iOriginalTrack < pOriginal->m_iNumTracks );
I don't understand how the AutoGen code works, but all I do know is
that the game works without this assert, but possibly in a way people
didn't want defined. Please can somebody (preferably Chris as he
says he's the only one who understands notedata :D) look at this
and figure out what i'm doing wrong.
I feel a bit uneasy taking out an assert to make things work....

stepmania/src/ScreenTitleMenu.cpp

@@ -247,6 +247,7 @@ void ScreenTitleMenu::HandleScreenMessage( const ScreenMessage SM )
 			case GAME_PUMP:		GAMESTATE->m_CurStyle = STYLE_PUMP_VERSUS;			break; 
 			case GAME_EZ2:		GAMESTATE->m_CurStyle = STYLE_EZ2_SINGLE_VERSUS;	break; 
 			case GAME_PARA:		GAMESTATE->m_CurStyle = STYLE_PARA_SINGLE;			break; 
+			case GAME_DS3DDX:		GAMESTATE->m_CurStyle = STYLE_DS3DDX_SINGLE;			break; 
 			default:	ASSERT(0);
 			}