move_base example feedback v1

[malwaru]

1. The TF between base_link and odom flickers, so I see the robot model moving between two spots on the map (for half a second). This is more noticeable if you set a 2D pose estimate in rviz (in which case the particle cloud from amcl moves, but not the robot model)

2. In the global and local costmap parameters, I think the fixed frame should be map, not odom. Maybe related, but I don't see a local costmap in rviz.

3. the SDF file for the world is hard-coded in environment_test_world.py; I guess you can pass it as a parameter in the launch file, or use rospkg.RosPack.get_path to get the package path

4. the amcl launch file points to a map that doesn't exist