Small changes to chen_modules.py, parameter_dict_A431.py, and test_egfr.py.  Added file to run all modules, egfr_and_apoptosis_exec.py.  Currently trying to simulate all the modules at once fails with a clang error (Segmentation fault: 11) that I think may be caused by the c file that contains the ODEs having a length>the maximum 4095 characters allowed by C99 standard.  Not sure this is the source of the error though.