stage_ros is incompatible with the "wander" stage controller

[sloretz]

Stage has a "wander" controller for position models that moves them around with crude obstacle avoidance. These do not move when using stage_ros because it sets the speed of all ModelPosition instances to zero in the WorldCallback() line 424.

I want to use the wander controller on some "position" models in a stage world for dynamic obstacles. For the time being I've hacked some code to only call SetPosition on the first robot.

It would be very cool if I could configure stage_ros to only control certain robots. Stage models can have names so maybe a list of robot names?