* origin/rtd-test:
Disable RTD pdf format due to exceeded capacity
Add RTD pdf format
Add RTD yaml config file
Remove some Bro usages in main TOC entries
Remove "contents" Sphinx directive usages
Add a `make livehtml` target
Use sourcecode Sphinx directive more widely
Use Sphinx RTD theme for user manual
Replace some code-block Sphinx directives
Remove unused Sphinx extensions
Remove broxygen Sphinx integration
Remove Sphinx btest integrations and tests
Fix a Sphinx deprecation
These are all changes required to build documentation from a static
Sphinx tree (e.g. on Read the Docs)
