Release Cantera 3.1.0

[speth]

Changes proposed in this pull request

This PR includes all the final changes for the release of Cantera 3.1.0. Cantera/cantera-website#263 should be merged at the same time as this PR.

• Update URLs based on the new organization of pages on the Cantera website that will take effect with the Cantera 3.1 release.
• Change deployment of docs to match the revised website structure
  • In addition to deploying docs built on the main branch to https://cantera.org/dev, this will also deploy docs built on future commits to the 3.1 branch to https://cantera.org/3.1.
  • Updates to maintenance branch docs are automatically committed to the api-docs repo for archival purposes
• Update version info in installation instructions
• Set version to 3.1.0

If applicable, fill in the issue number this pull request is fixing

Resolves #1748 (in conjunction with #1807)

Checklist

• The pull request includes a clear description of this code change
• Commit messages have short titles and reference relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• Style & formatting of contributed code follows contributing guidelines
• The pull request is ready for review

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.54%. Comparing base (a60ff4d) to head (7d9e81c).
Report is 11 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1809   +/-   ##
=======================================
  Coverage   73.54%   73.54%           
=======================================
  Files         383      383           
  Lines       54653    54653           
  Branches     9105     9105           
=======================================
+ Hits        40194    40197    +3     
+ Misses      11460    11458    -2     
+ Partials     2999     2998    -1     

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[ischoegl]

🎉 … thank you, @speth. This all looks good to me!