fixed map panning
fixed map panning

The panning feature of the map has been reimplemented. The pan speed
scales with the zoom scale of the map.

BCLab-UNM/SwarmBaseCode-ROS,BCLab-UNM/SwarmBaseCode-ROS,BCLab-UNM/SwarmBaseCode-ROS,BCLab-UNM/SwarmBaseCode-ROS,BCLab-UNM/SwarmBaseCode-ROS,BCLab-UNM/SwarmBaseCode-ROS