[Major] GpioBridge is now a singleton

src/main/java/ch/eitchnet/beaglebone/GpioBridge.java

@@ -19,7 +19,17 @@ public class GpioBridge {
 	private Thread thread;
 	private volatile boolean run;
 
-	public GpioBridge() {
+	private static final GpioBridge instance;
+
+	static {
+		instance = new GpioBridge();
+	}
+
+	public static GpioBridge getInstance() {
+		return instance;
+	}
+
+	private GpioBridge() {
 		this.cache = new HashMap<>();
 		this.listeners = Collections.synchronizedMap(new HashMap<>());
 	}

src/main/java/ch/eitchnet/beaglebone/GpioBridgeTest.java

@@ -25,7 +25,7 @@ public class GpioBridgeTest {
 
 		Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
 
-		GpioBridge gpioBridge = new GpioBridge();
+		GpioBridge gpioBridge = GpioBridge.getInstance();
 
 		System.out.println("Preparing pins...");
 		greenBtn = gpioBridge.getGpio(Pin.P8_07, Direction.IN).setLabel("Green");