Add PlayerState::GetDisplayedPosition() and PlayerState::GetDisplayedTiming()

which returns the dispalyed position and timing (based on the timing display
switch in the editor), so less copy n paste in ArrowEffects and NoteField.

src/PlayerState.h

@@ -41,6 +41,9 @@ public:
 
 	// Music statistics:
 	SongPosition m_Position;
+	
+	const SongPosition &GetDisplayedPosition() const;
+	const TimingData   &GetDisplayedTiming()   const;
 
 	/**
 	 * @brief Change the PlayerOptions to their default.