Fix a bunch of Sphinx warnings

[yck011522]

Fixing a bunch of doc string related error messages. This will allow real doc-string problems to be more visible. At the moment there is 13 warning messages:

C:\Users\leungp\Documents\GitHub\compas_fab\src\compas_fab\backends\kinematics\analytical_inverse_kinematics.py:docstring of compas_fab.backends.kinematics.analytical_inverse_kinematics.AnalyticalInverseKinematics.inverse_kinematics:22: ERROR: Unexpected indentation.
C:\Users\leungp\Documents\GitHub\compas_fab\src\compas_fab\backends\kinematics\analytical_inverse_kinematics.py:docstring of compas_fab.backends.kinematics.analytical_inverse_kinematics.AnalyticalInverseKinematics.inverse_kinematics:23: WARNING: Block quote ends without a blank line; unexpected unindent.
C:\Users\leungp\Documents\GitHub\compas_fab\src\compas_fab\backends\pybullet\planner.py:docstring of compas_fab.backends.pybullet.planner.PyBulletPlanner.add_attached_collision_mesh:18: WARNING: Inline literal start-string without end-string.
C:\Users\leungp\Documents\GitHub\compas_fab\src\compas_fab\backends\pybullet\planner.py:docstring of compas_fab.backends.pybullet.planner.PyBulletPlanner.add_attached_collision_mesh:18: WARNING: Inline literal start-string without end-string.
C:\Users\leungp\anaconda3\envs\cf-dev\Lib\site-packages\roslibpy\ros.py:docstring of roslibpy.ros.Ros.blocking_call_from_thread:7: ERROR: Unexpected indentation.
C:\Users\leungp\anaconda3\envs\cf-dev\Lilooking for now-outdated files... b\site-packages\roslibpy\ros.py:docstring of roslibpy.ros.Ros.call_sync_service:9: ERROR: Unexpected indentation.
C:\Users\leungp\anaconda3\envs\cf-dev\Lib\site-packages\roslibpy\ros.py:docstring of roslibpy.ros.Ros.off:6: ERROR: Unexpected indentation.
C:\Users\leungp\Documents\GitHub\compas_fab\src\compas_fab\robots\reachability_map\reachability_map.py:docstring of compas_fab.robots.reachability_map.reachability_map.ReachabilityMap:15: CRITICAL: Unexpected section title.

Links
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C:\Users\leungp\Documents\GitHub\compas_fab\src\compas_fab\robots\trajectory.py:docstring of compas_fab.robots.trajectory.Trajectory:4: CRITICAL: Unexpected section title.

Attribute
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C:\Users\leungp\Documents\GitHub\compas_fab\docs\examples\07_reachability_map.rst:5: WARNING: duplicate label examples_kinematics, other instance in C:\Users\leungp\Documents\GitHub\compas_fab\docs\examples\06_backends_kinematics.rst
C:\Users\leungp\Documents\GitHub\compas_fab\docs\examples\07_reachabilinone found
pickling environment... ty_map\03_rp_2D.rst:3: WARNING: Duplicate explicit target name: "link to full script".
done
checking consistency... done
preparing documents... done
writing output... [100%] license                                               inematicsom_urdfreset_planning_sceneshed_collision_mesh
C:\Users\leungp\Documents\GitHub\compas_fab\docs\backends\pybullet.rst:24: WARNING: undefined label: compas:robots
C:\Users\leungp\Documents\GitHub\compas_fab\docs\backends\ros.rst:157: WARNING: undefined label: compas:robots
generating indices... genindex py-modindex done
writing additional pages... search done
copying images... [100%] _images/compas_fab.png                                t_override.jpgpg
copying downloadable files... [100%] examples/05_backends_pybullet/files/01_add_attached_collision_mesh.pya.ghx
copying static files... done
copying extra files... done
dumping search index in English (code: en)... done
dumping object inventory... done
build succeeded, 13 warnings.

What type of change is this?

• Bug fix in a backwards-compatible manner.
• New feature in a backwards-compatible manner.
• Breaking change: bug fix or new feature that involve incompatible API changes.
• Other (e.g. doc update, configuration, etc)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I added a line to the CHANGELOG.md file in the Unreleased section under the most fitting heading (e.g. Added, Changed, Removed).
• I ran all tests on my computer and it's all green (i.e. invoke test).
• I ran lint on my computer and there are no errors (i.e. invoke lint).
• I added new functions/classes and made them available on a second-level import, e.g. compas_fab.robots.CollisionMesh.
• I have added tests that prove my fix is effective or that my feature works.
• I have added necessary documentation (if appropriate)

[yck011522]

This PR is based on the #394 because a bunch of error is present in the V-Rep part, since that is going away, I'm not fixing those mistakes.

#394 should be reviewed and merged before this one.

[yck011522]

@chenkasirer or @gonzalocasas
Maybe if anyone of you wants to review this.

[gonzalocasas]

Besides the minor comments below, it LGTM!