Store cities' arguments in the output file

[gonzaponte]

We want to keep the parameters used in each city and propagate them as we go through the chain. This way we always know what configuration was used without doubts or having to rely on other files.
This is done in nexus already, which stores the macros under /MC/configuration. I propose doing the same and keeping them under /some_descriptive_group_name/city_name.