Adding a numerics IDS to store convergence and errors of various actors

[TimSlendebroek]

The idea is to make it a structure like::

dd.numerics[N]
                           .name :: String
                           convergence[N]
                                                        .name :: String
                                                        .error:: Real
                                                        .error_per_iteration:: Vector{Real}
                                                        grid [N]
                                                                       .name
                                                                       ..error:: Real
                                                                       .error_per_iteration:: Vector{Real}

                           .converged :: Bool.  :: expression :: with logic check if each is converged