This work builds an extractor for the data in the CertStream in order to
save it. It builds itself from the previous work, so extensions and
flags can be added to the structures. The work in `utils` is basically a
big extractor for the data taking advantage of the JSONq library.
Currently, there is not refactoring and the "chains" are not saved
because they need additionnal computation which will come in a later
commit.
