add a 4-argument addContactListener() method (addresses issue #37)

Author: stephengold

MinieLibrary/src/main/java/com/jme3/bullet/PhysicsSpace.java

@@ -331,6 +331,23 @@ public void addContactListener(ContactListener listener) {
         manager.addContactListener(listener, true, true, true);
     }
 
+    /**
+     * Register the specified listener for immediate contact notifications.
+     *
+     * @param listener the listener to register (not null, alias created)
+     * @param doEnded true to enable {@code onContactEnded()} callbacks for the
+     * listener, false to skip them (default=true)
+     * @param doProcessed true to enable {@code onContactProcessed()} callbacks
+     * for the listener, false to skip them (default=true)
+     * @param doStarted true to enable {@code onContactStarted()} callbacks for
+     * the listener, false to skip them (default=true)
+     */
+    public void addContactListener(ContactListener listener, boolean doEnded,
+            boolean doProcessed, boolean doStarted) {
+        Validate.nonNull(listener, "listener");
+        manager.addContactListener(listener, doEnded, doProcessed, doStarted);
+    }
+
     /**
      * Add the specified PhysicsJoint to this space.
      *