Also in this commit:
* Sync CI scripts with other projects
* Modernize docs/conf.py
* Replace redmine_issue extension with sphinx.ext.extlinks
* Minor updates to docs/doxygen.conf.in
* Cleanup README.md and INSTALL.rst
Refs: #5095
Change-Id: I614e876e6aed73659f4f4cea01813f4604599263