Added AnimComposer.hasAction() method

jme3-core/src/main/java/com/jme3/anim/AnimComposer.java

@@ -98,6 +98,10 @@ public class AnimComposer extends AbstractControl {
         return action;
     }
     
+    public boolean hasAction(String name) {
+        return actions.containsKey(name);
+    }
+
     public void makeLayer(String name, AnimationMask mask){
         Layer l = new Layer();
         l.mask = mask;