disable clang-9 CI tests in c++2a mode because of the issues with com…

…parisons in chrono

update copyright years

update copyright years

change "std" status to "proposal" due to https:/wg21.link/p2141

Disable constexpr_ops test on MSVC

Update the docs

Update the docs

Update the docs

Docs for 1.0.4 (pre Boost-review version)

Clean up and update the docs