Integrate magnetometer into localization node

[VAM7686]

For some reason, the magnetometer is not integrated in our localization node, the ekf_localization_node. It is important to integrate the magnetometer measurements in order to ensure more accurate state estimation.

A simple way to visualize the inaccuracies caused by the lack of magnetometer integration is by:

1. roslaunch igvc_gazebo ramp_lane.launch
2. In gazebo rotate the robot about 45 degrees counter clockwise so it is facing in a different starting direction.
3. roslaunch igvc_navigation localization.launch
4. Open rviz and display the /ground_truth and /odometry/filtered topics. The difference between the ground truth and the state estimation should be evident and look something like this:

(green arrow is ground truth and red arrow is state estimation)

AC: Integrated magnetometer measurements in the ekf_localization_node.