move visualization-related publishers from HuberoPlannerROS to Visualization class

[rayvburn]

	/// @section Publishers
	/// @brief Global plan publisher (for visualisation)
	ros::Publisher g_plan_pub_;
	/// @brief Local plan publisher (for visualisation)
	ros::Publisher l_plan_pub_;
	/// @brief Explored trajectories PCL publisher (for visualisation)
	ros::Publisher traj_pcl_pub_;
	/// @brief TTC trajectories PCL publisher (for visualisation)
	ros::Publisher ttc_pcl_pub_;
	/// @brief Publishes the potential field generated by the cost function, ref: base_local_planner::MapGridVisualizer
	ros::Publisher cost_grid_pcl_pub_;