Change behaviour for changing volume/pan on Piano

All the selected notes are changed by default for the 3 possible events:

- Mouse dragging the volume/pan meter
- Rolling the mouse wheel over the meter
- Double-clicking the meter

The user can still change each note individually by holding alt before
performing the desired action

include/Note.h

@@ -204,6 +204,7 @@ public:
 		return m_detuning;
 	}
 	bool hasDetuningInfo() const;
+	bool withinRange(int tickStart, int tickEnd) const;
 
 	void createDetuning();