Audio Engine volume bug & small update

Fixed a bug where the volume change would be ignored if the sound was fading
Added SoundEngine::GetMusicVolume
Removed volume factor
Removed unused SetListenerVelocity

src/AudioLib/MaSoundInstance.h

@@ -42,7 +42,7 @@ public:
 
 	bool IsFading() const;
 
-	void Update(float volumeFactor = 1.0f);
+	void Update();
 
 private:
 	std::string m_Identity;