adding monitored_nav to topological_navigation.launch. 

default is monitored_nav without recovery behaviours
I think the best ways are either to use ros private namespace params or use the python arg parser. The former is probably the most ROS-friendly approach. From `rosed topological_utils dummy_topological_navigation` I have

```
if __name__ == '__main__':
    rospy.init_node('dummy_topological_navigator')
    size = rospy.get_param('~size', 5)
    sim_times = rospy.get_param('~simulate_time', False)
    map_name =  rospy.get_param('~map', None)
    if map_name:
        rospy.loginfo('simulating map: %s' % map_name)
```