Using the stdlib's http.cookie module, cookies are now stored as one
"Set-Cookie" header per line. Previously, the aiohttp.CookieJar's save() and
load() methods were used (which use pickling).
ILIAS apparently changes the order of the fields as it sees fit, so we
now try to parse *every* column, starting at from the right, as a date.
The first column that parses successfully is then used.