Add static constructor methods for easy-of-use

Java/src/main/java/com/gildedrose/behavior/quality/DefaultQualityBehavior.java

@@ -9,6 +9,10 @@ public class DefaultQualityBehavior implements QualityBehavior {
     public static final int DEFAULT_QUALITY_DECREASE = 1;
     public static final int FASTER_QUALITY_DECREASE = 2;
 
+    public static DefaultQualityBehavior newInstance() {
+        return new DefaultQualityBehavior();
+    }
+
     @Override
     public void processQualityUpdate(Item item) {
         decreaseQuality(item);

Java/src/main/java/com/gildedrose/behavior/quality/IncreasingQualityBehavior.java

@@ -7,6 +7,10 @@ public class IncreasingQualityBehavior implements QualityBehavior {
     public static final int MAX_QUALITY_LEVEL = 50;
     public static final int MIN_QUALITY_LEVEL = 0;
 
+    public static IncreasingQualityBehavior newInstance() {
+        return new IncreasingQualityBehavior();
+    }
+
     @Override
     public void processQualityUpdate(Item item) {
         increaseQuality(item);

Java/src/main/java/com/gildedrose/behavior/sellin/DefaultSellInBehavior.java

@@ -4,6 +4,10 @@ import com.gildedrose.Item;
 
 public class DefaultSellInBehavior implements SellInBehavior {
 
+    public static DefaultSellInBehavior newInstance() {
+        return new DefaultSellInBehavior();
+    }
+
     @Override
     public void processSellInUpdate(Item item) {
         decreaseSellIn(item);