[web-request] handle default language earlier
We now read language negotiation header at initialisation time (previously done
during ``set_session``). This simplify the set_session code for later reworking.
There is no change in behavior, the user selected language continue to overwrite
the one picked from the header/default when applicable.
related to #2503918
# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s entity's classes"""