Add Boost program_options command-line program and config file parsing demo examples

[ElectricRCAircraftGuy]

Ex: https://github.com/boostorg/program_options/blob/develop/example/multiple_sources.cpp

Tutorial: https://www.boost.org/doc/libs/1_75_0/doc/html/program_options/tutorial.html

My answer: https://stackoverflow.com/questions/7125666/what-is-boostprogram-optionsnotify-for/66865258#66865258

Bring in the Boost code as a git submodule (I think).

Plan on using Bazel to compile it? Maybe? Or, maybe I can just use gcc all at the command-line in a raw fomat (preferred?), or: possibly just use cmake or something--whatever Boost comes with in the source code (for build files) or recommends in their instructions.