message: rtabmap.launch: Exposed ground_truth_frame_id parameter
diff: <arg name="frame_id" default="camera_link"/> <!-- Fixed frame id, you may set "base_link" or "base_footprint" if they are published -->
  <arg name="odom_frame_id" default=""/> <!-- If set, TF is used to get odometry instead of the topic -->
  <arg name="map_frame_id" default="map"/>
  + <arg name="ground_truth_frame_id" default=""/> <!-- e.g., "world" -->
  + <arg name="ground_truth_base_frame_id" default=""/> <!-- e.g., "tracker", a fake frame matching the frame "frame_id" (but on different TF tree) -->
  <arg name="namespace" default="rtabmap"/>
  <arg name="database_path" default="~/.ros/rtabmap.db"/>
  <arg name="queue_size" default="10"/>
  <param name="frame_id" type="string" value="$(arg frame_id)"/>
  <param name="map_frame_id" type="string" value="$(arg map_frame_id)"/>
  <param name="odom_frame_id" type="string" value="$(arg odom_frame_id)"/>
  + <param name="ground_truth_frame_id" type="string" value="$(arg ground_truth_frame_id)"/>
  + <param name="ground_truth_base_frame_id" type="string" value="$(arg ground_truth_base_frame_id)"/>
  <param name="odom_tf_angular_variance" type="double" value="$(arg odom_tf_angular_variance)"/>
  <param name="odom_tf_linear_variance" type="double" value="$(arg odom_tf_linear_variance)"/>
  <param name="wait_for_transform_duration" type="double" value="$(arg wait_for_transform)"/>
  