added yaml files with mean sample parameters for testing, edited readme

[ManuelaRunge]

can be run via i.e.
python runScenarios.py -rl Local -r IL -mc extendedcobey_200428_means.yaml -c spatial_EMS_experiment_means.yaml -e extendedmodel_EMS.emodl -n "test_means_normal"

Note, the spatial yaml has only mean values (uniform 1 value), while for the main model parameter yaml extendedcobey_200428_means.yaml - has two versions mean values (uniform 1 value) and extendedcobey_200428_means_normal.yaml - mean values using a normal distribution and some variation.

These yaml files are for testing model parameter, model structure changes and potentially fitting to reduce number of samples to run. The mean values were informed from the baseline simulation with 600 samples.