Get quaternion from packet

[RonaldEnsing]

This PR implements getting the quaternion from the packet directly to compose the ROS Imu message.

This means that conversions between RPY and quaternions are no longer needed in the ROS node.

The quaternion is reported as s, x, y, z, according to the Spatial Dual Reference Manual.

As far as I understand the result should be equal, unless e.g., the system_state_packet contains a processed state estimation, and the quaternion_orientation_packet contains a raw measurement.