tables::mtuple::operator
1) Assignment operator
template <typename... Ks, typename... Vs>
mtuple<std::pair<Ks,Vs>...>::operator=(
const mtuple<std::pair<Ks,Vs>...>& other
)
2) Move assignment operator
template <typename... Ks, typename... Vs>
mtuple<std::pair<Ks,Vs>...>::operator=(
mtuple<std::pair<Ks,Vs>...>&& other
)