WIP oauthclient/accounts: permanent login support

* Sets session.permanent when then user marks 'remember me'.

* Allows configuration of oauth login to set if session should
  be permanent.

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
It's correct - see https://github.com/inveniosoftware/invenio/pull/2589/files#diff-6ffd71577ca22eab7dfaa7ad0bcc2704R56