base: fix for wsgi PATH_INFO handling

• Addresses issue with url encoded arguments in Flask routes. E.g. for route /collection/<name> the view argument name was not unescaped when accessed by /collection/Books%20%26%20Reports on Apache and this led to error during lookup in database. (closes #1823)

Reported-by: Petr Broz <petr.broz@gmail.com>
Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>