v1.8
Moved central C++ features to universal header file
A few unrelated code improvements
Renamed file cxx_polyfill.h to cxx_type_traits_polyfill.h
Addressed the chicken-and-egg problem with <optional>, <string_view>
Removed "Pointer" suffix from some pointer variables
Removed superfluous include
Corrected comment on `pass_extracted_fn_to`
Iterate schema objects instead of 'storage impl'