Cleanup native audio plugin

PlayWallCore/src/main/java/de/tobias/playpad/audio/AudioCapability.java

@@ -11,10 +11,10 @@ public class AudioCapability {
 	public static final AudioCapability EQUALIZER = new AudioCapability("EQUALIZER", Equalizeable.class);
 	public static final AudioCapability SOUNDCARD = new AudioCapability("SOUNDCARD", Soundcardable.class);
 
-	private String nameKey;
-	private Class<? extends AudioFeature> clazz;
+	private final String nameKey;
+	private final Class<? extends AudioFeature> clazz;
 
-	private static List<AudioCapability> audioCapabilityList;
+	private static final List<AudioCapability> audioCapabilityList;
 
 	static {
 		audioCapabilityList = new ArrayList<>();

PlayWallPlugins/PlayWallPluginNativeAudio/src/main/java/de/tobias/playpad/audio/windows/NativeAudioWinHandler.java

@@ -26,11 +26,11 @@ public class NativeAudioWinHandler extends AudioHandler implements Soundcardable
 	static final String SOUND_CARD = "SoundCard";
 
 	private NativeAudio audioHandler;
-	private ObjectProperty<Duration> durationProperty;
-	private ObjectProperty<Duration> positionProperty;
+	private final ObjectProperty<Duration> durationProperty;
+	private final ObjectProperty<Duration> positionProperty;
 
 	private static Thread positionThread;
-	private static List<NativeAudioWinHandler> playedHandlers = new ArrayList<>();
+	private static final List<NativeAudioWinHandler> playedHandlers = new ArrayList<>();
 	private static final int SLEEP_TIME_POSITION = 50;
 
 	static {

PlayWallPlugins/PlayWallPluginNativeAudio/src/main/java/de/tobias/playpad/plugin/NativeAudioPathType.java

@@ -7,7 +7,7 @@ public enum NativeAudioPathType implements ContainerPathType {
 
 	AUDIO(PathType.LIBRARY.getFolder() + "/Audio");
 
-	private String folder;
+	private final String folder;
 
 	NativeAudioPathType(String folder) {
 		this.folder = folder;