Move some player-specific data out of the bloated GameState class.

Have gameplay objects hold a PlayerState pointer instead of a PlayerNumber and indexing back into GameState.
This will simplify off-screen players (e.g. CPU ghosts, network replicated human players, >2 players using one NoteField)

stepmania/src/PlayerOptions.h

@@ -92,7 +92,7 @@ struct PlayerOptions
 		SCROLL_CENTERED,
 		NUM_SCROLLS
 	};
-	float GetReversePercentForColumn( int iCol ); // accounts for all Directions
+	float GetReversePercentForColumn( int iCol ) const; // accounts for all Directions
 
 	/* All floats have a corresponding speed setting, which determines how fast
 	 * PlayerOptions::Approach approaches. */