Gradient-base algorithms are disabled

in Fit/Kernel/Kernel.cpp

Kernel::minimize(...)

    if (m_minimizer->requiresResiduals())
        throw std::runtime_error(
            "Error in Kernel::minimize: the chosen minimizer requires residuals computation. "
            "Please use FitObjective::evaluate_residuals with this minimizer.");

It is unclear to me why GSLNLSMinimizer and Minuit2:Fumili were deativated in such a way.

Looks also strange why gradients are called "residuals".

added Fit label

changed the description