[web/request] use a picklable Counter object for tab index counters Related to #1381328.

[web/auth] The auth retriever's authenticated() callback takes a session, not a cnx We don't have a cnx at that point.

[test] Fix the query-log-file test Testing this functionality in a CubicWebTC is awkward because the wrapping happens in handle_request, which tests basically bypass (they call core_handle directly, and do their own magic for linking the request with a cnx). The test method worked when ran on its own, but not together with the rest of the test class. So use a CubicWebServerTC instead, which goes through the whole stack.

[doc/book] spelling fixes in security tutorial