Remove Boost dependency

[GhostlyDark]

Requires testing and code reviews. Currently requires C++17.

[Narann]

Thanks !

I’m generally not in favor of recent langage feature support, but requiring C++17 saves the main dependency problem we have with this repo.

From this matrix, std::filesystem is available since :

• GCC libstdc++ 8 (2018)
• Clang libc++ 7 (2018)
• MSVC STL 19.14 (2018)
• Apple Clang 11.0.0 (2019)
• IBM Open XL C/C++ for AIX 17.1.1 (?)
• Embarcadero C++ Builder 10.3 (?)