Use Parameter set object to store Marrmot parameters

[sverhoeven]

Now you have to do

model = ewatercycle.models.MarrmotM14(version="2020.11", forcing=forcing_validation)
cfg_file, cfg_dir = model.setup(
    maximum_soil_moisture_storage=parameters[0],
    threshold_flow_generation_evap_change=parameters[1],
    leakage_saturated_zone_flow_coefficient=parameters[2],
    zero_deficit_base_flow_speed=parameters[3],
    baseflow_coefficient=parameters[4],
    gamma_distribution_chi_parameter=parameters[5],
    gamma_distribution_phi_parameter=parameters[6],
    initial_upper_zone_storage=0.9*parameters[0],
    initial_saturated_zone_storage=0.9*parameters[0],
)

it would be nice to do

parameter_set = ewatercycle.parameter_sets.get_parameter_set("marrmot14-rhine")
model = ewatercycle.models.MarrmotM14(version="2020.11", forcing=forcing_validation, parameter_set=parameter_set)
cfg_file, cfg_dir = model.setup()