Tests: Check that a repo is clean

See merge request sed-rennes/sharelatex/python-sharelatex!33

pulling gitignored file musn't delete them

Closes #33

See merge request sed-rennes/sharelatex/python-sharelatex!32

We changed the behavior of `git slatex new` (we don't rely on the
git/config when calling it anymore). So we need to pass some extra info
on the command line (username, password, auth_type) otherwise we'll be
prompted and the test fails.

Set default URL for overleaf.irisa.fr
Client: set more precise loggin infor

[irisa] Add support for local login

See merge request sed-rennes/sharelatex/python-sharelatex!28

One can passe a session to authenticate with
alternatively one can set a session to the objet (setter)
alternatively the session we'll be built on demand when getting it
(getter)

This follow the heads-up of

https://gitlab.inria.fr/sed-rennes/sharelatex/python-sharelatex/-/issues/29