- Changed the thruster ID values to correspond to the current thruster
  connection setup.
- Changed FRV thruster direction from -1Z to +1Z.
- Changed PID values for the sub. Values are still not ideal and will be
  adjusted over the next few testing sessions.
- Changed the identifier for the USB to CAN board's USB to serial
  converter.
- Changed tcp address for the depth sensor, imu, and dvl connection
  scripts to their ip addresses instead of their DNS names (there is an
issue with the DNS server in the network box, or in the lab, or both).
- Made changes to the sub8.urdf.xacro for gazebo to avoid URDF inertia
  warning.
- Added bag_debugging_controller.launch file which is a launch file to
  record bags for debugging the PID controller on the sub.

- Added documentation page about PID controller containing information
about the bag_debugging_controller.launch file and some tips for how to
tune the PID controller.
- Reverted subjugator_launch/readme.md changes to reflect moving to a
new documentation page.
- Modified adaptive controller values to remove commented out kd values.

- Another URDF xacro fix has been applied to the URDF xacro file using
these ROS forum posts as reference:
https://answers.ros.org/question/393006/urdf-link-not-properly-fixed-to-world/,
https://answers.ros.org/question/192817/error-msg-the-root-link_base-has-an-inertia-specified-in-the-urdf-but-kdl/.
NOTE: This is not a complete fix yet. I'm getting a tf republisher error
that 'base_link' and 'map' do not have a connection with TF having 2+
unconnected trees. Additionally, gazebogui does not work since
the /gzclient/set_physics_properties service is not advertised (even
though /gazebo/set_physics_properties is).

Note that these are changes I made on my local PC that I'm getting
around to submitting.
- Added documentation for the nav tube including calibration for the
IMU.
- Added documentation for filling the watercooling loop (missing
emptying loop and adding photos for clarification).
- Made edits to testing procedures to reflect materials we ended up
using at different points + reiteration of red battery tube cap.
- Modified MOTD to reflect changes in local documentation.
- Modified magnetic hardsoft compensation script for changes in
matplotlib and numpy structure.