Update docs

[rajat2004]

1. Add Python API docs
2. Add links for ArduPilot usage (Closes Documentation: ArduPilot support #2686)
3. Update CHANGELOG.md
4. Add more info about Logs in FAQs
5. Fix indentation
6. Note about installation in C drive (Windows install issue #2697)
7. Fix RL page link (closes Unable to view the Reinforcement Learning tutorial by Ashish Kapoor #2745)
8. Add PyMarkdown extras extension - requires pip install pymdown-extensions

I'm not quite sure as to how to link to the html page from the markdown files other than just having it in the nav bar and mentioning in the markdown to go to them through the github.io page nav bar. Better ways to add it to the docs are very much welcome

The 5th commit fixes the code-blocks and FAQs ordering in https://microsoft.github.io/AirSim/build_linux/, and numbering of steps in https://microsoft.github.io/AirSim/unreal_custenv/
It, however, causes the content of .uproject in the custom env page to be like the ones in the Linux build page. I thought it's okay considering it fixes the step numbering which I think is more imp
Let me know if I should change it back

Edit: The above is no longer a problem, the extras extension contains superfences which handles fenced codeblocks, and gives a nice-looking border around them, do test it out!

Just using build_docs.sh and opening the index.html file will lead to links opening to the file server and not the html files directly. Run mkdocs serve to see how it will actually work

[rajat2004]

The main improvement to be done is to automate the docs build, that will prevent out-of-date docs at different places and save maintainer effort
Though that will most likely require an encrypted token key for say Travis to push to the gh-pages branch

Without automating the doc build and deploy, I think it'll kind of defeat the entire point of having auto-generated docs from docstrings

[rajat2004]

@madratman @saihv Could you have a look at this? Main addition here required is to enable automatic docs build using say Travis or Github Actions. I'm not sure as to what method is used currently, is it run build_docs.sh from master branch, then mkdocs gh-deploy?
Note that this will most likely involve creating a new token with push access to the Airsim repository, and adding that to Travis

[rajat2004]

Added a commit which runs a currently non-existent deploy_docs.sh script on Travis master
I'm not sure of how the docs are updated, but probably mkdocs gh-deploy isn't used since it erases all history on the branch.

Maybe something like mkdocs/mkdocs#1082? I went for Travis instead of a Github Action since we also Sphinx in the mix to build the Python API docs
There are several other ways to write the script, just need to find one which works best

[rajat2004]

This will conflict with #2712, will be better to merge that first
Also, the last 2 commits could be separated out into a different PR since setting up auto deployment will probably take some time, if it's preferable to get the other docs updates in first

Travis setup needs to be looked at

[rajat2004]

Moved Travis commits to #2749

[rajat2004]

/azp run microsoft.AirSim

[azure-pipelines]

Commenter does not have sufficient privileges for PR 2658 in repo microsoft/AirSim

[madratman]

/azp run microsoft.AirSim

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[rajat2004]

@madratman @saihv Is it possible to get this one merged anytime soon? The API reference would be very helpful for figuring out problems when using the Python APIs, and not require a deep-dive into the code to figure things out

[madratman]

mkdocs and sphinx can't be run together due to a tornado version conflict b/w mkdocs and msgpack-rpc-python (needed for api docs)
I had therefore added a build_api_docs.sh in Pythonclient/ sometime back

[madratman]

I'll copy generated api docs to a dir build_docs/ (not docs/)