doc!: organize and rename examples, and additional small fixes

[c-dilks]

Addresses the following issues:

• [x] ROOT macro example should call Algorithm::Stop()
• [x] python examples are overwriting the iguana namespace documentation
• [x] consistent coloring in setup.md bullets
• [x] order the examples for a new user

Possible breaking change

• all executable names now use underscores instead of hyphens
  • the ROOT macro example cannot have hyphens
  • prevents doxygen from creating non-existent Python "namespaces"
• example names are now of the format:

  iguana_ex_[LANGUAGE]_[NUMBER]_[NAME]

  where:

• [LANGUAGE] is the programming language
• [NUMBER] is the example number (optional), for ordering examples for new users
  • examples without [NUMBER] are for certain, possibly language-specific, use cases
• [NAME] is a descriptive name for the example