Updates to the documentation - Maxim - #2869

Part of the updates to the documentation.

The docs_merge branch is an intermediate branch to cross-review changes before opening a PR into pytorch_dlc.

In particular, I review the following doc files:

• docs/course.md
• docs/standardDeepLabCut_UserGuide.md
• docs/Overviewof3D.md
• docs/deeplabcutlive.md
• docs/ModelZoo.md
• docs/recipes/UsingModelZooPupil.md
• docs/gui/PROJECT_GUI.md
• docs/quick-start/single_animal_quick_guide.md
• docs/beginner-guides/manage-project.md
• docs/beginner-guides/labeling.md
• docs/beginner-guides/Training-Evaluation.md
• docs/beginner-guides/video-analysis.md
• docs/convert_maDLC.md
• docs/recipes/BatchProcessing.md
• docs/recipes/DLCMethods.md
• docs/recipes/ClusteringNapari.md
• docs/recipes/OpenVINO.md
• docs/recipes/pose_cfg_file_breakdown.md
• docs/recipes/publishing_notebooks_into_the_DLC_main_cookbook.md
• docs/MISSION_AND_VALUES.md
• docs/Governance.md
• docs/roadmap.md

Moreover, I copy the fix to build jupyter books locally from niels/docs. This is a temporary commit, it will be picked from niels/docs when combining the changes.

Also, I add additional reference points to docs reviewed in niels/docs to reference here, this will need to be merged.

Also, I introduce a temporary fix to create_pretrained_project() by forcing it to create fake metadata with TensorFlow as backend engine. This will need to be fixed once Pytorch compatibility is added to create_pretrained_project().

I also remove docs/recipes/MegaDetectorDLCLive.md from _toc.yml, since the MegaDetector app is not online anymore.

Finally, I update the .rst files to point to the right methods for correct doctring insertion.