Ioopt cache - integration with ioopt corrected

Adding:

• The option "~version 3" on the Python call through OCaml (on Debian/Ubuntu, "python" is Python 2 per default)
• The file "perm_cache_with_pinocchio.json" which is the output of ioopt (in order to run the searchs).

This branch name can be removed afterward (if possible).