add boolean facedown in Card

src/main/java/de/hsfulda/onses/models/Card.java

@@ -11,6 +11,7 @@ public class Card {
 
     private Color color;
     private Value value;
+    private boolean facedown;
 
     public enum Color {
         RED, BLUE, GREEN, YELLOW, BLACK;
@@ -41,6 +42,15 @@ public class Card {
         return this.value;
     }
 
+    public boolean isFacedown() {
+        return facedown;
+    }
+
+    public Card setFacedown(boolean facedown) {
+        this.facedown = facedown;
+        return this;
+    }
+
     public PropertyChangeSupport listeners() {
         if(this.listeners == null) {
             this.listeners = new PropertyChangeSupport(this);