rename exp path and name

Currently ExpSetup has parameters exp_date and experiment_path. The real exp path is set to experiment_path (or cwd if not given) + <exp_date>_network_<sampling> (sampling only if hourly). This originates from the call from command line with the starting date as name for the experiment. But if would be much better, to be able to give it a custom name instead of date. Maybe is sufficient to just rename the parameter, or think about another solution.