Add a function `extract_job_zip`

[micheles]

It must work for Aristotle calculations. It must export a job.zip archive (only for GEM users) containing:

1. job.ini
2. rupture.csv
3. gsim_lt.xml
4. site_model.csv
5. exposure.xml and exposure.csv
6. vulnerability functions.xml
7. taxonomy_mapping.csv

This is a lot of work, but the hard part is checking that indeed by running the job.zip one can recover the results of the original Aristotle calculation.