Visualize IMU data

[Thinking-Dragon]

• Create a new component called inertial-measurements (run ng g c inertial-measurements --module app) ;
• Inject the ROSService in the constructor of your component (constructor(ros: ROSService) {) ;
• For each information in sensor_msgs/imu, add an attribute in your component (ex. linearAccelerationCovariance: Vector3) ;
• Create a method which will be called every time a message is received (ex. private handleMessage(message: Imu) { ... }) ;
  This method should take every member of the message and put their values in the attributes of your component.
• In the constructor, subscribe to the topic ;
  Ex. this.imuDataTopic = ros.getTopic( ... ).subscribe((message: Imu) => this.handleMessage(message)).
• In the view (.html), display the inertial measurements you received (ex. {{ linearAccelerationCovariance }}).

* Reference for the sensor_msgs/imu ROS message type:
http://docs.ros.org/en/melodic/api/sensor_msgs/html/msg/Imu.html