Added Duration::min ()/max() and notes about making it constexpr and deprecated Duration::kMin/kMax
Added Duration::min ()/max() and notes about making it constexpr and deprecated Duration::kMin/kMax

SophistSolutions/Stroika,SophistSolutions/Stroika,SophistSolutions/Stroika,SophistSolutions/Stroika,SophistSolutions/Stroika