Recovery behaviors / costmap cleanup

[jubeira]

The local costmap isn't cleaned quite well yet.
E.g. in this case, the laser can see through the obstacles, but they are not cleared in the local costmap.

Recovery behaviors also need some testing and tuneup.

[jubeira]

Update: #119 loads recovery behaviors as plugins.
move_base confirms that the plugins are properly loaded, but there is still something missing: the costmaps aren't cleared properly when the rosout output says it should be cleared.