add dispose methods to behavior tree library and cloner

fix libgdx#12

gdx-ai/src/com/badlogic/gdx/ai/btree/TaskCloner.java

@@ -26,4 +26,10 @@ public interface TaskCloner {
 	 * @return the cloned task */
 	public <T> Task<T> cloneTask (Task<T> task);
 
+	/**
+	 * Free task previously created by this {@link TaskCloner}
+	 * @param task task to free
+	 */
+	public <T> void freeTask(Task<T> task);
+
 }

gdx-ai/src/com/badlogic/gdx/ai/btree/utils/BehaviorTreeLibrary.java

@@ -151,5 +151,16 @@ public void registerArchetypeTree (String treeReference, BehaviorTree<?> archety
 	public boolean hasArchetypeTree (String treeReference) {
 		return repository.containsKey(treeReference);
 	}
+
+	/**
+	 * Dispose behavior tree obtain by this library.
+	 * @param treeReference the tree identifier.
+	 * @param behaviorTree the tree to dispose.
+	 */
+	public void disposeBehaviorTree(String treeReference, BehaviorTree<?> behaviorTree){
+		if(Task.TASK_CLONER != null){
+			Task.TASK_CLONER.freeTask(behaviorTree);
+		}
+	}
 
 }

gdx-ai/src/com/badlogic/gdx/ai/btree/utils/BehaviorTreeLibraryManager.java

@@ -80,5 +80,14 @@ public <T> BehaviorTree<T> createBehaviorTree (String treeReference) {
 	public <T> BehaviorTree<T> createBehaviorTree (String treeReference, T blackboard) {
 		return library.createBehaviorTree(treeReference, blackboard);
 	}
+
+	/**
+	 * Dispose behavior tree obtain by this library manager.
+	 * @param treeReference the tree identifier.
+	 * @param behaviorTree the tree to dispose.
+	 */
+	public void disposeBehaviorTree(String treeReference, BehaviorTree<?> behaviorTree){
+		library.disposeBehaviorTree(treeReference, behaviorTree);
+	}
 
 }