Record bag files for Unit tests

Recording bag file and converting to CSV

• Path information-

Path	Offset (x,y)	Orientation(Gazebo)	Path-Length
Straight	100,280	0	200
Circular	165,280	0	100
Sinusoidal	100,280	0.74	190
Eight	100,280	0.74	370

• Run the following command to record the bag file-

rosbag record /amcl_pose /astroid_path /base_pose_ground_truth /clicked_point /clock /cmd_delta /cmd_vel /cross_track_error /plot /prius /rosout /rosout_agg /tf /tf_static -O pathname_constant_velocity

• The initial position of the car must be 100,280.
• You can change the initial position of the car from demo.launch file.
• Do not change the initial offsets of the path. They are already set properly
• Following are the topic names which is used for the data plotting-

/Cross_track_error.linear.x  :Cross-track Error
/Cross_track_error.linear.y  :Difference in bot orientation and nearest point tangent
/Cross_track_error.angular.x :Maximum cross-track error(won't include initial offset)
/Cross_track_error.angular.y :Average Cross-track error(won't include initial offset) 
/Cross_track_error.linear.z  :Distance along path

/prius.brake : (braking between 0 and 1)
/prius.throttle : (acceleration between 0 and 1)
/prius.steer : (steering_angle between -1 and 1) mapped to (-30 deg to +30 deg)

• Here is the link for the python script to convert bag file into CSV file.
• All the paths have to be recorded for three different constants each having velocities 2.5, 5, 10 m/s.