Write detailed Diff-Drive-Controller documentation to make all the interfaces understandable.

[destogl]

Please help where TODO are added.

This is not yet finished, but provides an initial structure.

[RichardvdK]

Can you switch base_frame_id and odom_frame_id? The descriptions do not cohere now.

[codecov-commenter]

Codecov Report

Merging #371 (f87a70d) into master (e7f9962) will decrease coverage by 5.79%. The diff coverage is 20.65%.

@@            Coverage Diff             @@
##           master     #371      +/-   ##
==========================================
- Coverage   35.78%   29.98%   -5.80%     
==========================================
  Files         189        7     -182     
  Lines       17570      737   -16833     
  Branches    11592      422   -11170     
==========================================
- Hits         6287      221    -6066     
+ Misses        994      161     -833     
+ Partials    10289      355    -9934     

Flag	Coverage Δ
unittests	29.98% <20.65%> (-5.80%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...de/diff_drive_controller/diff_drive_controller.hpp	100.00% <ø> (ø)
...ontroller/test/test_load_diff_drive_controller.cpp	12.50% <0.00%> (ø)
diff_drive_controller/src/odometry.cpp	42.16% <11.11%> (ø)
...ive_controller/test/test_diff_drive_controller.cpp	17.62% <12.08%> (ø)
diff_drive_controller/src/speed_limiter.cpp	46.55% <13.33%> (ø)
...troller/include/diff_drive_controller/odometry.hpp	20.00% <20.00%> (ø)
...iff_drive_controller/src/diff_drive_controller.cpp	32.67% <24.89%> (ø)
...ory_controller/src/joint_trajectory_controller.cpp
...ers/joint_trajectory_controller/src/trajectory.cpp
...ollers/test/test_joint_group_effort_controller.cpp
... and 192 more