Fixing camera_info_manager topic so that it conforms to the standard namespace

This bug made it into the releases, but should really be fixed. 

According to the [ROS camera spec](http://wiki.ros.org/camera_drivers), the camera info topic should be on `camera/set_camera_info`, but instead with gscam, it's just `set_camera_info`. This patch fixes that, but it might break code (mostly calibration scripts) for people who have been using gscam already.