Correct CMake script. Improve C++ language feature selection

[scivision]

• CMake already required CMake >= 3.13, it would error immediately without that
• Use canonical way to set per-language compiler options
• Use simpler, modern CI configuration
• use C++ [[fallthrough]] that most compilers have
• use C++ [[noreturn]] that most compilers have

[greg7mdp]

Thanks a lot for the great PR @scivision