place => entity
frontier place => boundary
many variables that switch from snake_case to camelCase
=> induces many problems of uniformity in the API and is very confusing; have fun.

export of xrefs in csv and json formats

Ability to parse v2 model with JSON extra-data.
Provide low-level functions used by get_statistics to provide a proper API.

sphinx-argparse module requires the object parser before the call of parse_args()