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>
I guess, you can add it here: https://github.com/inveniosoftware/invenio/pull/2589/files#diff-46a958a5e99e38d6281e62011756224fR88